A local environmental group says the transformer explosion at the Indian Point nuclear facility last month caused more damage than the company claims.

The group, Riverkeeper, says the contents of the 20,000-gallon capacity transformer have seeped into the ground and the Hudson River. While it says it is unable to pinpoint the exact quantity of the oil spilled into the water, the group says the number of gallons may be in the thousands.

Entergy Corporation, which owns Indian Point, says only 100 gallons were spilled and the cleanup was done immediately.

Riverkeeper is urging the Nuclear Regulatory Commission to determine the cause of the explosion.