About 400 gallons of oil leaked into the ground surrounding a Harvard Museum of Comparative Zoology research facility last week, according to its director, Lyman Professor of Biology Andrew A. Biewener.

Biewener said that only a small portion of the leak had spread into the wetlands surrounding the Concord Field Station (CFS) and that he did not expect the spill to affect the environment.

The CFS, which he said is located in a "fairly remote" area outside Boston, studies local animal movements and plant structures.

The oil seeped into an underground bunker, where pumps designed to empty the basin of groundwater released it outside the CFS.

The leak was reported Friday afternoon.

However, CFS administrators did not realize the gravity of the leak until Monday, according to Biewener, when they discovered that the oil had spread.

"We were lucky that we caught it when we did," he said.

"It was only when we realized that it had moved off-site to a greater distance than we had expected that we realized immediate reaction was needed," he added.

CFS has hired a national contractor, Clean Harbors Environmental, to clean the area and recover the oil. Biewener estimated that the cleanup would be completed by the fall.

Biewener said that the regularly inspected tank was still under warranty and that CFS planned to investigate whether the tank was faulty.

Biewener met yesterday with the director of Harvard's Environmental Health and Safety department, Joe Griffin, to discuss the cleanup. The U.S. Environmental Protection Agency, Massachusetts Department of Environmental Protection and Bedford conservation commission were also notified.

A spokesman for Clean Harbors said that the company was legally bound to refer inquiries to Harvard.

--Staff writer Daniel K. Rosenheck can be reached at rosenhec@fas.harvard.edu.