An oil tanker leaked about 30 000 gallons of crude into the Delaware River late on Friday, worrying local environmentalists and causing a section of the river to be closed to commercial traffic, Coast Guard officials said on Saturday.

The spill covered 20 square miles of water by Saturday morning and the Coast Guard said it had contracted clean-up help from three firms. ?We take every spill very seriously?, said a Coast Guard chief Petty Officer.

The Athos 1, sailing under the Cypriot flag, was being pulled into the Citgo oil refinery in Paulsboro, New Jersey, across the river from suburban Philadelphia when tug boat crew members noticed the ship listing 8 degrees to the left, Coast Guard Petty Officer John Edwards said. The crew members then noticed crude had leaked out, and the ship lost power.

Local environmentalists said they were concerned about the fish and more than 100 species of birds that breed in or migrate through the area.