diff --git a/gguf-tools.c b/gguf-tools.c
index 91dfd44..aa012f9 100644
--- a/gguf-tools.c
+++ b/gguf-tools.c
@@ -2,7 +2,10 @@
 #include <stdlib.h>
 #include <ctype.h>
 #include <string.h>
+#include <assert.h>
+
 #include "gguflib.h"
+#include "sds.h"
 
 /* ========================== Utility functions  ============================ */
 
@@ -201,6 +204,93 @@ void gguf_tools_split_mixtral(int expert_id, const char *mixtral_filename, const
         if (!skip)
             gguf_append_kv(output,key.name,key.namelen,key.type,value,value_len);
     }
+
+    /* Now it's time to copy the tensors. We need to copy all the shared
+     * tensors (between the different experts), but only a set of
+     * expert-specific tensors corresponding to the expert ID the user
+     * wants to extract. */
+    struct tensor_to_copy {
+        sds dest_name;          // Tensor name in the output file.
+        gguf_tensor orig_info;  // Original tensor info.
+        uint64_t dest_offset;   // Destination offset in output file.
+        uint64_t size;          // Tensor total bytes.
+    };
+
+    uint32_t num_tensors = 0;
+    uint32_t max_tensors = 2048;
+
+    struct tensor_to_copy *tensors =
+        malloc(sizeof(struct tensor_to_copy)*max_tensors);
+    if (tensors == NULL) {
+        perror("Allocating tensors info array");
+        exit(1);
+    }
+
+    /* Scan Mixtral tensors looking for the ones we need to copy
+     * in the output model. */
+    gguf_tensor tensor_info;
+    while (gguf_get_tensor(mixtral,&tensor_info)) {
+        assert(num_tensors < max_tensors);
+
+        char tn[1024]; // Tensor name as null terminated string.
+        snprintf(tn,sizeof(tn),"%.*s",(int)tensor_info.namelen, tensor_info.name);
+
+        /* The tensor is a feed-forward tensor? We want to copy only
+         * the ones of our expert ID. */
+        if (strstr(tn,".ffn_") != NULL && strstr(tn,".ffn_norm") == NULL) {
+            char match[32];
+            snprintf(match,sizeof(match),".%d.weight",expert_id);
+            char *match_ptr = strstr(tn,match);
+            if (match_ptr == NULL) {
+                printf("Skipping tensor %s\n", tn);
+                continue; // Skip this tensor.
+            }
+
+            /* We need to remove the .<id>. from the name. */
+            size_t taillen = strlen(match_ptr);
+            memmove(match_ptr,match_ptr+2,taillen+1);
+        }
+
+        /* Create the entry for this tensor. Later we will scan all our
+         * entries and append data to our output tensor. */
+        tensors[num_tensors].dest_name = sdsnew(tn);
+        if (tensors[num_tensors].dest_name == NULL) {
+            perror("Allocating test tensor name");
+            exit(1);
+        }
+        tensors[num_tensors].orig_info = tensor_info;
+        tensors[num_tensors].size = tensor_info.bsize;
+        num_tensors++;
+    }
+
+    /* Now we need to set the offset for our destination tensors. As
+     * we calculate the offsets, we can emit the tensors information
+     * section as well. */
+    uint64_t tensor_off = 0; // Tensor offsets are relative to data section,
+                             // so we start at offset 0.
+    for (uint32_t j = 0; j < num_tensors; j++) {
+        /* Align offset. */
+        tensor_off += gguf_get_alignment_padding(mixtral->alignment,tensor_off);
+        tensors[j].dest_offset = tensor_off;
+        if (gguf_append_tensor_info(output,tensors[j].dest_name,strlen(tensors[j].dest_name),tensors[j].orig_info.ndim,tensors[j].orig_info.dim,tensors[j].orig_info.type,tensor_off) == 0)
+        {
+            perror("Failed to append tensor info");
+            exit(1);
+        }
+        tensor_off += tensors[j].orig_info.bsize;
+    }
+    printf("Output file: after writing tensors info, file size is: %llu\n", output->size);
+
+    /* Finally, append the tensors weights. */
+    for (uint32_t j = 0; j < num_tensors; j++) {
+        printf("Writing tensor %s\n", tensors[j].dest_name);
+        if (gguf_append_tensor_data(output,tensors[j].orig_info.weights_data,
+            tensors[j].orig_info.bsize) == 0)
+        {
+            perror("Failed to append tensor data");
+            exit(1);
+        }
+    }
     exit(0);
 }
 
diff --git a/gguflib.c b/gguflib.c
index 6cf5b83..c409aee 100644
--- a/gguflib.c
+++ b/gguflib.c
@@ -451,7 +451,7 @@ int gguf_append_kv(gguf_ctx *ctx, const char *keyname, uint64_t keylen, uint32_t
 
 /* Append tensor metadata (but not the actual tensor weights data) to the
  * GGUF file identified by 'ctx'. */
-int gguf_append_tensor(gguf_ctx *ctx, const char *tensorname, uint64_t namelen, uint32_t num_dim, uint64_t *dim, uint32_t type, uint64_t offset)
+int gguf_append_tensor_info(gguf_ctx *ctx, const char *tensorname, uint64_t namelen, uint32_t num_dim, uint64_t *dim, uint32_t type, uint64_t offset)
 {
     if (write(ctx->fd,&namelen,sizeof(namelen)) != sizeof(namelen)) return 0;
     if (write(ctx->fd,tensorname,namelen) != (ssize_t)namelen) return 0;
@@ -467,32 +467,14 @@ int gguf_append_tensor(gguf_ctx *ctx, const char *tensorname, uint64_t namelen,
     return 1;
 }
 
-/* Append tensor data enforcing the GGUF file aligment. The user must specify
- * an offset that requires no more than ctx.alignemnt-1 padding bytes starting
- * from the current offset (this means that this function should be called
- * sequentially for all the tensors we want to store, after we already
- * computed the right offset for all the tensors). Also the offset must be
- * aligned. Otherwise the function will fail returning 0. On success, 1 is
- * returned. The function will take care to add the padding required to
- * start writing the tensor at the specified offset. */
-int gguf_append_tensor_data(gguf_ctx *ctx, uint64_t offset, void *tensor, uint64_t tensor_size) {
+/* Append tensor data enforcing the GGUF file aligment.
+ * The function will take care to add the padding required to start writing
+ * the tensor at an alignment multiple. */
+int gguf_append_tensor_data(gguf_ctx *ctx, void *tensor, uint64_t tensor_size) {
     char padding_data[1024] = {0};
     assert(sizeof(padding_data) >= ctx->alignment);
 
-    /* Is the offset aligned? */
-    if (offset % ctx->alignment) {
-        errno = EINVAL;
-        return 0;
-    }
-
-    /* We expect the offset of the context to be already where this tensor
-     * should be stored, minus the padding. */
-    if (offset < ctx->off || offset - ctx->off >= ctx->alignment) {
-        errno = EINVAL;
-        return 0;
-    }
-
-    uint64_t padding = gguf_get_alignment_padding(ctx->alignment,offset);
+    uint64_t padding = gguf_get_alignment_padding(ctx->alignment,ctx->size);
     if (write(ctx->fd,padding_data,padding) != (ssize_t)padding) return 0;
     if (write(ctx->fd,tensor,tensor_size) != (ssize_t)tensor_size) return 0;
     gguf_remap(ctx);
diff --git a/gguflib.h b/gguflib.h
index 173df19..cf10367 100644
--- a/gguflib.h
+++ b/gguflib.h
@@ -174,8 +174,8 @@ void gguf_do_with_value(gguf_ctx *ctx, uint32_t type, union gguf_value *val,
                                      uint64_t array_len));
 void gguf_print_value(gguf_ctx *ctx, uint32_t type, union gguf_value *val, int full);
 int gguf_append_kv(gguf_ctx *ctx, const char *keyname, uint64_t keylen, uint32_t type, void *val, uint64_t len);
-int gguf_append_tensor(gguf_ctx *ctx, const char *tensorname, uint64_t namelen, uint32_t num_dim, uint64_t *dim, uint32_t type, uint64_t offset);
-int gguf_append_tensor_data(gguf_ctx *ctx, uint64_t offset, void *tensor, uint64_t tensor_size);
+int gguf_append_tensor_info(gguf_ctx *ctx, const char *tensorname, uint64_t namelen, uint32_t num_dim, uint64_t *dim, uint32_t type, uint64_t offset);
+int gguf_append_tensor_data(gguf_ctx *ctx, void *tensor, uint64_t tensor_size);
 uint64_t gguf_get_alignment_padding(uint64_t alignment, uint64_t offset);
 
 #endif