MILWAUKEE (AP) - A truck carrying monkey droppings and algae from the Milwaukee County Zoo spilled its smelly contents across the junction of two busy highways Tuesday, closing the roads and tying up midday traffic.

"I think it's comparable to any sort of sewage," zoo spokeswoman Jennifer Diliberti said. "One of the zookeepers said from a scale of one to 10, the smell's a nine."

The accident happened when a latch broke on a tank holding the dark, sludge-like waste, said Kim Brooks, a spokeswoman for the Milwaukee County Sheriff's Department.

Eastbound Interstate 94 and southbound U.S. 45/Interstate 894 were closed for about four hours after the 10:45 a.m. local time spill.