UPDATED at 11:25 a.m. with search for truck.

ST. LOUIS COUNTY • The source of a smelly chicken-parts spill that shut down Highway 40 (Interstate 64) in west St. Louis County for hours Tuesday evening remains a mystery, police say.

Chesterfield Police Lt. Steve Lewis says police are still looking for the truck that dropped a giant load of chicken parts in the eastbound lanes near the Timberlake Manor Parkway exit about 4:30 p.m., forcing a massive cleanup that blocked traffic for hours.

"We still have police cars that stink, too," Lewis said.

Lewis said the only description police have is that the truck may have had the word, "American" on it.

"Whoever dropped the chicken stuff did not stop," Monarch Fire Protection District Fire Marshal Roger Herin said Tuesday evening. "It's a mess."

Herin said cars that drove through the spill tracked the parts for about a mile.

"It's slick for quite a ways," Herin said. "It smells like rotten meat."

Authorities believe the truck driver was unaware of the spill at the time.