Puerto Rican officials said today they were never told about the mistaken use of radioactive shells during Navy target practice on an outlying island.

In disclosing that a Marine fighter jet accidentally fired 263 armor-piercing shells loaded with depleted uranium at a practice range on Vieques Island earlier this year, the Navy said Thursday it had informed all appropriate federal and local agencies.

Puerto Rican nationalists opposed to the U.S. Navy presence allege that, during the decades that part of Vieques has been used as a target range, the island has become contaminated with radioactivity. They say this contributes to a cancer rate among the 9,300 inhabitants that is twice the Puerto Rican average.

Navy spokesman Roberto Nelson said a fighter jet was mistakenly loaded either at Mayport, Fla., or Norfolk with depleted uranium shells. Their use on Vieques is forbidden by federal and local laws, as well as Navy regulations.

The "isolated, one-time incident" was reported to the local Environmental Quality Board and the federal Nuclear Regulatory Commission well within the required week, Nelson said.

But Gov. Pedro Rossello's office said he was not notified, and Secretary of State Norma Burgos expresses skepticism about the claims.

Burgos later told a special commission studying the Navy's effect on Vieques that environmental board chairman Hector Russe told the commission's technical committee today that he never received notification from the Navy about the accident.

Nelson said the accident occurred in early March. Roger Hannah, a spokesman for the Nuclear Regulatory Commission, said a Navy report filed March 5 said the accident occurred Feb. 19.

The military uses depleted uranium because it is extremely dense and can pierce thick armor. Hannah said "there is virtually no risk to public health and safety" because depleted uranium has low radiation and the area where it was released is a restricted military zone. Nelson also said there was no health hazard.

Puerto Ricans remain angered at an April 19 accident in which a Navy jet missed its target at the range and dropped two 500-pound bombs that killed a civilian security guard.