Railroad crews tried to contain a 120,000-gallon fuel spill threatening a waterfowl refuge Wednesday and got help from beavers.

The jet and diesel fuel spilled after an Alaska Railroad freight train derailed Monday 40 miles south of Fairbanks. Seven cars, each holding 20,000 gallons, ripped open, spilling fuel into beaver ponds to either side of the track.Despite efforts to dam it, one pond was draining fuel into a creek and the 500,000-acre Minto Flats Wildlife Refuge downstream, said Pete McGee, a regional supervisor for the state Department of Environmental Conservation.

More fuel probably would have run into the creek if not for the beaver dams, said Al Townsend, a biologist for the state Department of Fish and Game.

Crews put absorbent booms across the dams and used suction machines to skim fuel from the placid water.

Environmental officials had no immediate estimate of the threat to wildlife in the boggy, conifer-covered area, a prime nesting area for waterfowl. But when asked about the effect on the beavers, Townsend drew a finger across his throat.

The cause of the derailment wasn't immediately known.

The train, with a crew of three, was going about 40 mph, carrying fuel to Anchorage from the Mapco Alaska Petroleum Inc. refinery in the town of North Police, said railroad spokeswoman Vivian Hamilton. No one was injured in the accident.