Cannot remove VNET

When I execute...

PS C:\> Remove-AzureRmVirtualNetwork -ResourceGroupName BCServerLAX -Name BCServerLAX

I got...

Remove-AzureRmVirtualNetwork : Operation returned an invalid status code 'BadRequest'
At line:1 char:1+ Remove-AzureRmVirtualNetwork -ResourceGroupName BCServerLAX -Name BCS ...+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+ CategoryInfo          : CloseError: (:) [Remove-AzureRmVirtualNetwork], CloudException+ FullyQualifiedErrorId : Microsoft.Azure.Commands.Network.RemoveAzureVirtualNetworkCommand

I can remove this VNET neither by the Portal nor by Azure PowerShell.