BAYONNE, N.J. (AP) _ It may take two months to clean 260,000 gallons of heavy heating oil that leaked from a grounded British tanker into a commercial waterway, the Coast Guard said Friday.

The Coast Guard said it had received reports of grapefruit-size tar balls as far as 15 miles away, coming ashore along Sandy Hook and Breezy Point, the points that flank the mouth of New York Harbor.

About 9,000 gallons of the industrial fuel has been recovered so far, said Coast Guard Capt. Robert North, adding that usually just 15 percent to 20 percent of a spill is recaptured.

North is overseeing the cleanup that began when the BT Nautilus ran aground early Thursday morning while docking in Bayonne.

The remainder of the oil will either dissipate or sink in the Kill Van Kull, a shipping channel between and Staten Island, N.Y. and an industrial stretch of New Jersey shoreline, officials said.

The Coast Guard, and the New York and New Jersey attorney's general offices were all investigating the spill. Civil and criminal charges were considered, said Judith Yaskin, New Jersey Commissioner for the Environment.

The accident, one of several significant oil spills in the New York Harbor this year, boosted the amount spilled in the area to more than 1 million gallons, or four times the 1989 total, the Coast Guard said. That is less than one-tenth the size of the catastrophic Exxon Valdez spill in Alaska's pristine Prince William Sound.

Coast Guard Rear Adm. Gene Henn said a board of inquiry will begin hearings Monday ''because we do not know if it is bad luck or a common thread that binds these incidents.'' The board is to make recommendations within ''weeks, not months,'' he said.

The tanker's first mate, Englishman Geoffrey Frederick Gregory, 52, faces state charges of operating a vessel while under the influence of either alcohol or drugs.

He pleaded innocent at his arraignment Thursday, was released on bail, and is to appear in Bayonne Municipal Court on June 12.

He is also charged with negligent discharge of a pollutant without a permit. The case is to be presented to a state grand jury in Trenton next week, said Christopher Florentz, a spokesman for Attorney General Robert J. Del Tufo, adding that the investigation is continuing.

Capt. James Sanial, in charge of the Coast Guard probe, said until the grounding there was no communication between Gregory, on duty at the front of the boat, and the captain and pilot in the ship's bridge.

The tanker's captain, Albert Ainscough, and docking pilot, Jim Naughton, were interviewed after the accident and said they noticed nothing amiss until the grounding.

Sanial said Naughton had no previous record of accidents.

''Ultimately, the master (captain) is always responsible for the ship. In actual practice, the pilot takes over (during docking),'' said Sanial.

More than 200 workers, including about 50 guardsmen, were cleaning the water and shores Friday, said North. The operation involved 47 vessels, including five boats equipped to skim oil from the surface, and a special Coast Guard oil spill response team from Mobile, Ala.

The tanker owner, Nautilus Motor Tanker of Gibraltar, has assumed responsibility for the cleanup, the Coast Guard said. The tanker is operated by Bulk Tanker Management of London and registered in Hong Kong.