Procedural Mesh with visible seams

Hello,

I've been working on proceduraly generated meshs with variable size. At the moment it's just a big square although I intend it to have holes in the future. Because I want those meshes to have multiple textures that I will get through WWW I am creating an atlas texture map (through PackTexture) but when I use the atlas, the squares' seams become noticeble. If I use a material with a single texture the seams are not visible. I've been searching the web but so far I have yet to figure out why this is happening.

The way I generate the mesh is: For each cell I create four vertices, then two triangles and finaly UV's. The UV's are based on the Rect list obtained from Texture.PackTextures.

The generating code:

 using UnityEngine;
 using UnityEditor;
 using System.Collections;
 
 public class MeshCreator : MonoBehaviour 
 {
     public Texture2D tex1;
     public Texture2D tex2;
     public Texture2D tex3;
     public Texture2D atlas;
     
     void Start () 
     {
         GetComponent<MeshRenderer>().enabled = false;
         Texture2D[] texs = new Texture2D[3];
         texs[0] = tex1;
         texs[1] = tex2;
         texs[2] = tex3;
         
         /*foreach (Texture2D texture in texs)  
         {
             string path = AssetDatabase.GetAssetPath(texture);
             //Debug.Log("path: " + path);
             TextureImporter textureImporter = AssetImporter.GetAtPath(path) as TextureImporter;
             textureImporter.isReadable = true;
             AssetDatabase.ImportAsset(path);
         }*/
         
         atlas = new Texture2D(0, 0);
         Rect[] texUVS = atlas.PackTextures(texs, 0, 2048);
         
         Mesh myMesh = new Mesh();
     
         int XX = 10, YY = 10;// 10x10 Mesh
         
         int CellSize = 2;
         
         int NumCells = XX * YY;
         int NumTriangles =  NumCells * 2; // Each cell has 2 tris
         
         int NumVertices = NumCells * 4; // Each cell has 4 verts
         int p0, p1, p2, p3;
                 
         Vector3[] verts = new Vector3[NumVertices];        
         int[] triangles = new int[NumTriangles * 3];        
         Vector2[] uvs = new Vector2[NumVertices];
         
         for(float c = 0, x = 0, z = 0, v = 0, t = 0; c < NumCells; c++, x+= CellSize, v+=4, t+=6)
         {
             
             if( c % XX == 0 && c > 0)
             {
                 x = 0;
                 z+= CellSize;
             }
             
             p0 = (int)v;
             p1 = (int)v + 1;
             p2 = (int)v + 2;
             p3 = (int)v + 3;
         
             verts[p0] = new Vector3(x,0,z);
             verts[p1] = new Vector3(x + CellSize,0,z);            
             verts[p2] = new Vector3(x,0,z + CellSize);
             verts[p3] = new Vector3(x + CellSize, 0, z + CellSize);
             
             // tri 1
             triangles[(int)t] = p2;
             triangles[(int)t+1] = p1;
             triangles[(int)t+2] = p0;
             
             // tri 2
             triangles[(int)t+3] = p2;
             triangles[(int)t+4] = p3;
             triangles[(int)t+5] = p1;
             
             
             //uvs 
             int r = Random.Range(0,(texUVS.Length ));
             uvs[p0] = new Vector2(texUVS[r].xMin, texUVS[r].yMin); //(0,0)
             uvs[p1] = new Vector2(texUVS[r].xMax, texUVS[r].yMin); //(1,0)
             uvs[p2] = new Vector2(texUVS[r].xMin, texUVS[r].yMax); //(0,1)
             uvs[p3] = new Vector2(texUVS[r].xMax, texUVS[r].yMax); //(1,1)
             
             
             /*
             uvs[p0] = new Vector2(0.0f, 0.0f);
             uvs[p1] = new Vector2(1.0f, 0.0f);
             uvs[p2] = new Vector2(0.0f, 1.0f);
             uvs[p3] = new Vector2(1.0f, 1.0f);*/
         }
         
         myMesh.vertices = verts;
         myMesh.triangles = triangles;
         myMesh.uv = uvs;
         
         myMesh.RecalculateNormals();
         myMesh.RecalculateBounds();
         
         myMesh.Optimize();
                 
         GetComponent<MeshFilter>().mesh = myMesh;
         GetComponent<MeshCollider>().sharedMesh = myMesh;
         GetComponent<MeshRenderer>().material.mainTexture = atlas;        
         
         GetComponent<MeshRenderer>().enabled = true;
         
         
     }
 }

And here's a picture using a black texture in the atlas:

Thank you.