I have a loop where I create a multiple Mesh with different geometry, because each mesh has one texture:

....
var geoCube = new THREE.CubeGeometry(voxelSize, voxelSize, voxelSize);
var geometry = new THREE.Geometry();

for( var i = 0; i < voxels.length; i++ ){
  var voxel = voxels[i];
  var object;
  color = voxel.color; 
  texture = almacen.textPlaneTexture(voxel.texto,color,voxelSize); 
  //Return the texture with a color and a text for each face of the geometry
  material = new THREE.MeshBasicMaterial({ map: texture });                       
  object = new THREE.Mesh(geoCube, material);

  THREE.GeometryUtils.merge( geometry, object );
}

//Add geometry merged at scene
mesh = new THREE.Mesh( geometry, new THREE.MeshFaceMaterial() );
mesh.geometry.computeFaceNormals();
mesh.geometry.computeVertexNormals();
mesh.geometry.computeTangents();

scene.add( mesh );  
....

But now I have this error in the javascript code Three.js

Uncaught TypeError: Cannot read property 'map' of undefined

In the funcion: function bufferGuessUVType ( material ) { .... }

Update:

Finally I have removed the merged solution and I can use an unnique geometry for the all voxels. Altough I think that If I use merge meshes the app would have a better performance...