Natural causes were responsible for the collapse of a mine operated by Akzo Nobel Salt Inc., a federal agency ruled, clearing the company of responsibility for the accident.

The federal Mine Safety and Health Administration attributed the March 1994 collapse to abnormalities in the rock layers above the 18-square-mile underground structure. David Park, the administrator in charge of investigations for MSHA, said there were weaknesses in limestone and shale layers that predisposed them to cause an accident.About 30 feet of the salt mine's roof collapsed, allowing groundwater to flow into the structure at rates up to 18,000 gallons a minute, the government report said. The cave-in occurred at a spot about 1,100 feet underground.

Although work at the Retsof mine resumed in April 1994, flooding will render the facility useless by the end of the summer. The Retsof mine is located 27 miles southwest of Rochester.

Some investigators had speculated that the company's yield-pillar mining technique caused the collapse. The yield-pillar technique uses a series of small pillars anchored by large blocks to hold up areas of the mine.

An executive with Akzo, of Clarks Summit, Pa., said the federal report showed the company took the proper steps to ensure safety in the facility.

"The MSHA study supports the fact that the small-pillar pattern had been used successfully in other test panels in the mine before it was used in the area that eventually was the site of the collapse," said G. Richard Thompson, senior vice president and chief administrative officer of Akzo.

Mr. Thompson said independent experts also found geological factors caused the collapse. No one was injured in the accident.

Akzo has filed a $261 million lawsuit against its insurers, Allianz Underwriters, for refusing to reimburse the mining company for its losses. Allianz is conducting its own investigation into the accident. It was not immediately clear how the federal report would affect that probe.

While Akzo was not required to do so, federal investigators suggested the company might have learned of the weaknesses in the rock above the mine if it tried some exploratory drilling of the area. Mr. Thompson said such drilling in search of geological abnormalities is not usually done in the salt mining industry.

Akzo is the world's largest producer of salt. The company is stockpiling

salt from the Retsof mine and is about to begin regulatory reviews for a $120 million mine in nearby Hampton Corners. That facility could start producing

salt by 1997.