The Navy is investigating a mercury leak that may have contaminated a well supplying water to the Naval Research Lab near Chesapeake Beach, Md., Navy officials said yesterday.

The leak of metallic mercury, the kind used in therometers, was discovered March 10, and use of the well was stopped immediately, according to Comdr. Bruce Bauer, of the Chesapeake Beach facility. The well is one of two that supply water to the approximately 200 residents and employes at the lab complex.

U.S. Environmental Protection Agency standards say that mercury up to the level of two part per billion in water is "acceptable."

"Above that level we would not recommend drinking it," said EPA toxicologist Kris Khanna.

A water sample taken last Monday at the Chesapeake Beach lab, about 25 miles southeast of Washington, showed the level of mercury in the affected well to be within the accepted standard, according to chemist William Fox, of the Naval Research Lab in Washington.

But Fox and other Navy officials said they did not know what levels of mercury were contained in water tested immediately after the leak was discovered.

More than 500,000 gallons of water already in the water supply system when the leak was discovered were drained, and the entire system was flushed out with fresh water, Bauer said.

However, the investigation of the leak is continuing until "there is an assurance of no mercury content in the main water supply of the division," according to a Navy spokesman.

The leak of about seven pounds of mercury "flow-meter," which measured water flowing from the 500-foot deep pressure well, the spokesman said.