Classes resumed this morning at Northeast Philadelphia High School, a day after students were sent home after 85 chickens were discovered roaming the building without hall passes.

Actually, they weren't supposed to be there at all. The incident appears to have been a prank - one that is now the subject of a police investigation.

"We're looking forward to a chicken-free day," said district spokesman Fernando Gallard.

Surveillance video shows four males entering the building at 9:30 p.m. Sunday, and the school building engineer discovered the first indication of the poultry liberation - a trail of what appeared to be sawdust - at 4:30 a.m. yesterday.

School officials canceled school for 3,600 students so that that facility on Cottman Avenue could be scrubbed down with a solution of bleach and water.

The chickens were taken to Fox Chase Farms in Philadelphia, where they are being cared for by the staff of Swenson Arts and Technology High School, which operates agricultural programs.

A state inspector is scheduled to check the birds for illnesses.

Once cleared, some of the chickens will be kept at the district's two farms if they are not claimed by an owner, Gallard said.

"They're egg-laying hens, so we'd make sure to put them to use," Gallard said.

Because the district can't keep all 85 hens, the remainder would be given to other farmers, he said.

Contact staff writer Robert Moran at 215-854-5983 or bmoran@phillynews.com.