By IAN URBINA
 
WASHINGTON, March 7 - The Organization of American States will reopen an investigation this week into the massacre of hundreds of peasants in 1981 at El Mozote, El Salvador, based on new forensic evidence found by anthropologists at the site, according to lawyers involved in the case.

More than 800 unarmed peasants were killed in December 1981 by soldiers from the Salvadoran Armed Forces at El Mozote, a village in the mountains of the Morazán region, near the country's southern border. The soldiers, from a battalion trained and equipped by the United States, accused the peasants of sympathizing with guerrillas. The O.A.S. is looking into whether the Salvadoran government approved the killings.

The decision to revisit one of the most gruesome events of the country's 12-year conflict will come as unwelcome news to the Salvadoran government, which has never conducted an independent and impartial investigation of its own.

The Inter-American Commission on Human Rights, a division of the O.A.S., is conducting the investigation. Recent efforts by lawyers in El Salvador to reopen the case, which was shelved in 2000, had repeatedly failed, even after a court ruling that year stripped protection under the national amnesty law from suspects in the most egregious human rights violations. "They say that we should put this behind us," said Rufina Amaya, the only resident of El Mazote known to have survived. "But we cannot forget what happened."

The evidence in the case comes from the work of an Argentine team of forensic anthropologists that completed its work in 2003. "What we found proved to be highly consistent with witness testimony of the incident," said Mercedes Doretti, a member of the forensic team.

She said 811 people were killed at El Mozote and surrounding hamlets. Most of the 271 bodies that the group exhumed were shot multiple times at close range, and 195 of them were children younger than 12, she said.

"The families of the dead have struggled for years to get justice," said Alejandra Nuño, a lawyer from the Center for Justice and International Law, an organization based in Washington that is representing many of the families of the dead. "This case may finally provide us what we've been unable to get from our own government."

The reopening of the case could hurt the candidacy of Francisco Flores, president of El Salvador from 1999 to 2004, for secretary general of the O.A.S.

Mr. Flores is running against José Miguel Insulza, Chile's interior minister, and Luis Ernesto Dérbez, Mexico's foreign minister. The election will be held by the end of March.

If the Commission on Human Rights finds enough evidence tying the Salvadoran government to the killings, the case will go to the Inter-American Court. Though it is unlikely that the court's decision would result in jail time for those involved, the court could demand that the government conduct an investigation of the incident and require payment of reparations to the families of those who died or disappeared.

At the time, Salvadoran officials denied reports of the massacre, first published in The New York Times and The Washington Post. Hoping to avoid a Congressional halt to aid to the Salvadoran military, officials of the Reagan administration also dismissed the reports. Families seeking justice in American courts for atrocities during the war have met with limited results in recent years.

On Monday, a State Department spokeswoman said she could not comment on the reopening of the investigation into El Mozote until it was officially announced.