Exception message : thread was being aborted.

Exception Message : Thread was being aborted.

I am getting above exception when running the application in prod server. I never get that exception in dev and in test environment. 
Could any please help me out. If there is anything wrong in the code. 

My code in vb.


  Try
                    Dim filePath As String = Request.QueryString("fn")
                    Response.ContentType = ContentType
                    Response.AppendHeader("content-disposition", "attachment; filename=" + Path.GetFileName(filePath))
                    Response.TransmitFile(filePath)
                    Response.Flush()

                    System.Threading.Thread.Sleep(1000)
                    If File.Exists(filePath) Then
                        File.Delete(filePath)
                    End If

                    Response.End()
                Catch ex As Exception
                    oUtility.WriteLog("Exception Message : " + ex.Message, True)
                    vm.stat = 2
                    vm.message = "Internal server error"
                    Throw
                End Try



My code in C#

  string filePath = Request.QueryString["fn"];
                        Response.ContentType = ContentType;
                        Response.AppendHeader("content-disposition", "attachment; filename=" + Path.GetFileName(filePath));
                        Response.TransmitFile(filePath);
                        Response.Flush();

                        System.Threading.Thread.Sleep(1000);
                        if (File.Exists(filePath))
                        {
                            File.Delete(filePath);
                        }
                        //response.writefile(filepath)
                        Response.End();