Cant access user account

Hi,

I have an issue with a couple of macs. After restarting the machine the only user available is the local administrator account. The macs have been added to our internal Active Directory for authentication but they are currently off the network. Our Mac tech did all the configuration however is un-contactable.

Is there a way to select the user account to use as login as we do not know the local admin password. There are no other options on the screen other than the password box.