CHEYENNE, Wyo. (AP) — The U.S. Bureau of Land Management says damage by a backhoe over an unknown amount of time led to a 25,000-gallon oil spill in the Powder River Basin in May.

BLM officials say Casper-based Belle Fourche Pipeline told them a backhoe nicked the 6-inch pipe during construction work but they don't know when that happened.

BLM officials say the pipeline became corroded where the damage occurred and that led to the May 19 spill 45 miles southeast of Buffalo.

Belle Fourche Pipeline Environmental Coordinator Bob Dundas declined to comment Tuesday when asked about the damaged pipe.

The oil flowed three miles down a gulley and officials burned the oil to clean it up. Documents obtained by The Associated Press show high levels of petroleum residue remained after the burn-off.