Mukwonago police say vandals smashed the windshields of the entire fleet of the city's 13 postal vehicles.

Postal inspector Lori Groen says the damage appears to have been inflicted either late Saturday or early Sunday. She says nothing was stolen.

She says a five-thousand dollar reward is being offered for information leading to a conviction.

A spokeswoman says the vehicles were either repaired or replaced Monday so there should be no delay in mail service.

The damage is estimated at more than 56-hundred dollars.

Mukwonago Police Chief Fred Winchowky says police have no suspects.

Groen says the post office hadn't received any threats and employees aren't aware of any problems with customers.