Two of the three Americans found dead at the wreckage of a helicopter shot down in El Salvador Wednesday may have been shot by leftist guerrillas after the crash, Pentagon and State Department officials said yesterday.

Administration spokesmen stopped short of formally accusing the Salvadoran rebels of executing the Army crew members, but said U.S. authorities found "dramatic" discrepancies in initial reports from the rebel troops fighting the U.S.-backed government.

The guerrillas, in a radio report Wednesday, asserted responsibility for shooting down the U.S. Army Huey UH-1 transport helicopter as it flew over a combat zone in eastern San Miguel province about 2:30 p.m. Wednesday. The guerrilla forces said the pilot and crew members died in the crash.

"The FMLN {Farabundo Marti National Liberation Front} says that the servicemen were found dead inside the aircraft," said Pentagon spokesman Pete Williams. "We have information to the contrary. . . All three had gunshot wounds to the head; two of these have no other apparent wounds."

Eyewitnesses interviewed at the scene told reporters that two of the soldiers were alive minutes after the crash. U.S. officials said their probe was continuing and that much of their initial information was based on second-hand accounts.

Salvadoran army officials found the bodies and removed them from the crash scene. No U.S. officials were present.

Asked if there were any indication that government troops may have shot the U.S. soldiers, one Pentagon official said, "I don't have enough information to rule it out. . . but we have no basis to give it credibility either."

U.S. officials also dispute the rebel claim that the helicopter was flying over a combat area. Williams and State Department spokesman Richard Boucher said the craft was following the Pan American Highway eastward from Ilopango airfield outside the capital city of San Salvador in south-central El Salvador to Soto Cano airbase in Honduras when it was shot down by small arms fire.

The vocal administration rebuttal to the rebel account occurs as President Bush nears Saturday's deadline for reporting to Congress on whether he plans to release an additional $42.5 million in military aid to the Salvadoran Army. Congress authorized Bush to give those funds to the Salvadoran government only if the rebels launched a military offensive that threatened the survival of the government or took other actions to prolong the conflict.

Boucher said the helicopter incident "will certainly be taken into consideration" in making the aid decision.

Sen. Patrick J. Leahy (D-Vt.), who helped write the legislation restricting the aid, said yesterday that if the rebels are responsible for executing the U.S. soldiers, "then they should probably get a retainer from the Salvadoran government for lobbying for increased military aid for El Salvador . . . because they, by their own actions, dramatically improve the chances of increased aid for El Salvador."

Interviews with Salvadoran peasants who said they arrived at the scene shortly after the crash muddied both the rebel and the U.S. versions of the incident. Some said the men died for lack of medical attention after the crash.

Silvio Mendez, who lives near the scene, told reporters he helped move two of the U.S. soldiers, who were wounded but alive, after the helicopter landed. Mendez and other witness said a third man died in the crash, according to a Reuters news service dispatch from El Salvador.

"One of them was asking for water, and another was saying, 'Don't move me,' " Mendez said. "When we came back with water for one of the gringos, {the helicopter} was already on fire and we couldn't get close."

Other witnesses said the Americans were dead of bullet wounds when Mendez and the others returned.

"If the initial eyewitness accounts prove to be accurate, at least two of these American servicemen were literally executed by the FMLN guerrillas," said one senior State Department official. "That would not be an act of war; that would be cold-blooded murder."

Pentagon spokesman Williams described the helicopter as on a routine transport mission when it was fired upon about five miles north of Lolotique in San Miguel province. The helicopter, whose passengers included the lieutenant colonel heading the Honduras-based transport operation, left the capital at about 1:40 p.m. local time Wednesday and was scheduled to arrive at Soto Cano airbase in Honduras at about 3 p.m.

The lieutenant colonel was ending a two-year tour in the region and had just introduced his replacement to officials in San Salvador before he boarded the helicopter back to Honduras, a state department official said.

U.S. officials reported the helicopter overdue at about 5:30 p.m., according to Williams. At about 6 p.m., the rebels issued a statement "taking credit for shooting down a U.S. helicopter," added Williams.

The U.S. military dispatched a fixed-wing airplane to search for the downed helicopter, but Salvadoran Army officials were the first to arrive at the scene, Williams said.

The bodies were transported to San Salvador where "they have been viewed by the U.S. military and are in U.S. custody now." A special military forensics team arrived in San Salvador yesterday to examine the bodies.

Williams said the helicopter was flying only about 50 feet above the ground because of new restrictions imposed to evade the SA-14 surface-to-air missiles now being used by guerrillas, who obtained some of the weapons from Nicaragua.

Staff correspondent Lee Hockstader contributed to this report from San Salvador.