Buffalo, N.Y. ? The FBI has released nearly 800 pages of material sought by attorneys for Leonard Peltier, an American Indian advocate serving two life sentences in the 1975 slayings of two FBI agents in South Dakota.

Responding to a Freedom of Information Act request, the FBI turned over 797 of the 812 pages collected by the Buffalo field office in the Peltier case. The FBI withheld 15 pages, citing exemptions allowed under the act for national security concerns and to protect the privacy of agents.

Peltier’s attorneys said Monday they would fight for the release of the withheld material.

“We’re going to argue that the exemptions are being improperly invoked,” said Buffalo attorney Michael Kuzma, who works with the Peltier defense team led by Bruce Ellison and Barry Bachrach.

Peltier supporters are seeking tens of thousands of pages from FBI documents from field offices nationwide as they fight to have his conviction overturned.

The Buffalo documents outline agents’ work as they checked with informants, including sources within the Seneca Indian Nation, and followed up on suspected Peltier sightings before his arrest, Kuzma said.

A Nov. 14, 1975, memo outlines an unidentified source’s claim that he saw Peltier at an Indian convention at a Buffalo hotel in October 1975, four months after the shooting. Another source believed he spotted Peltier in Steamburg, near the Senecas’ Allegany reservation, teaching Indian dances to women, Kuzma said.

Peltier was convicted of killing agents Ronald Williams and Jack Coler during a standoff on the Pine Ridge Indian Reservation in South Dakota.

Supporters have long campaigned to free Peltier, 59, claiming he was unfairly targeted because of his political activism.