One of four peacocks that wandered away from the Philadelphia Zoo and created a traffic jam on a nearby highway was found dead on that stretch of road on Thursday.

Zoo staffers had been working with authorities to try to locate the peacocks after they took a stroll along part of Interstate 76 about a mile (1.6 kilometers) from the zoo on Wednesday night. State police arrived and shut down two of the six lanes of traffic on the highway, causing backups for miles.

Police got the peacocks off the highway but were unable to capture them. The peacocks likely went to roost for the night, and the search was halted until daybreak Thursday.

Two teams of animal curators and keepers from the zoo and police officers circled the area where the peacocks were last seen. They also checked locations where the zoo teams thought the peacocks might explore.

The peacock found dead on the highway on Thursday likely had been hit by a car, zoo spokeswoman Dana Lombardo said.

The four peacocks were part of a larger flock that roams freely on the zoo's grounds and that is cared for by veterinary staff. The birds sometimes venture past the zoo's gates but normally return on their own, Lombardo said. They have a homing sense, and it's unusual for them to travel that far from the zoo, she said.

Zoo officials asked people not to approach the peacocks because they may be nervous being out of their normal environment. Instead, people who see the peacocks can send the location, day and time and a photo of the sighting if possible to peacocks@phillyzoo.org.