OAKLAND — No birds were killed in a wood chipper during a tree-trimming incident outside a downtown post office earlier this month, a U.S. Fish and Wildlife investigation has found.

Steve Martarano, a spokesman for the federal agency, said Tuesday that investigators made the determination after interviewing witnesses, reviewing a video and examining the contents of the wood chipper.

The finding confirms statements from Oakland police, the U.S. Postal Service and contractor Ernesto Pulido, who all said no birds were killed in the wood chipper during the May 3 trimming of trees surrounding the parking lot of the post office on 13th Street between Jackson and Alice streets.

However, five black-crowned herons, estimated to be 1 week to 3 weeks old, were hurt after falling some 25 feet from the trees as workers hacked away at branches. Outraged onlookers rescued the birds and eventually took them to International Bird Rescue in Fairfield. Last week, a spokesman for the center said the birds were in “good condition” after suffering scrapes and bruises from the fall. One bird also had a fractured beak.

Feds: No birds killed in wood chipper during Oakland tree trimming