The Navy has suspended indefinitely underwater explosions in the Chesapeake Bay after a blast Saturday killed about 800 pounds of trout, just two weeks after federal officials decided to resume the controversial testing.

Diane Palermo, a spokeswoman for the Naval Surface Warfare Center, said yesterday that the Navy probably will halt all testing until next year, after a thorough investigation of the program.

"It will be a while before we do any more testing," Palermo said. "I don't think we can do the kind of things we need to do this year."

On Friday, the Navy resumed the underwater tests of antisubmarine weapons, apparently without incident. Officials then reported that an eight-pound explosive device had killed four pounds of fish, far below the 80-pound kill limit set by the Maryland Department of Natural Resources.

The next day, however, a 3:10 p.m. blast in Anderson Bay, off Solomons Island, killed 800 pounds of fish, Palermo said.

Saturday's high fish kill set off renewed protests from charter fishermen and state officials. A blast in 150 feet of water near the mouth of the Patuxent River on Oct. 30 killed about 3,000 fish, officials said.

The Navy and state officials later agreed to limit tests to eight pounds of TNT-like explosives and to equip the test barge with sonar devices to detect fish.

Still, Navy officials yesterday were unable to explain why the state-of-art sonar equipment failed to detect the large schools of fish.

Rep. Roy Dyson (D-Md.) questioned the reliability of the Navy sonar equipment. "As a member of the Armed Services Committee, I know we have equipment that can just about detect anything," he said.