Two Oglala Sioux men whose deaths touched off Saturday's violence-marred protest walk to Whiteclay, Neb., apparently were last seen alive two days before their bodies were found, authorities said Wednesday.

Tribal police and the FBI disclosed the finding Wednesday in a press release that also announced a reward of up to $15,000 for information leading to the arrest and conviction of those who killed Wilson "Wally" Black Elk Jr., 40, and Ronald Hard Heart, 39.

It was the first new information in a week about the fate of the two men, whose bodies were found June 8 just inside the Pine Ridge Indian Reservation about a quarter of a mile north of Whiteclay.

A lack of public information about the case has fueled allegations by some Sioux that law enforcement officials may have been involved in the deaths. The deaths were also the catalyst for last Saturday's protest.

A second rally is planned Saturday.

In conversations with Pine Ridge reservation leaders Wednesday, Judi Morgan, executive director of the Nebraska Commission on Indian Affairs, said she has stressed the importance of keeping the second march "calm and peaceful."

Any violence could jeopardize a planned July 7 visit by President Clinton, she said. Clinton is slated to be on the reservation to speak about an economic development initiative.

"If we can't guarantee the president's safety, then the president probably won't come," Morgan said.

Wednesday's press release stated that Black Elk and Hard Heart reportedly were spotted walking north from Whiteclay to Pine Ridge, S.D., about 10:30 p.m. June 6, according to tribal Police Chief Stan Star Comes Out and James H. Burrus Jr., acting special agent in charge of the FBI's Minneapolis office.

Autopsies conducted in Rapid City, S.D., found that the deaths were homicides. Investigators have refused to describe wounds found on the bodies, but have said blood was found near them. Published obituaries had listed the date of death as June 7.

Black Elk and Hard Heart were found in a grassy depression beyond a barbed-wire fence west of South Dakota Highway 407, the two-mile main road from Pine Ridge to Whiteclay.

"All investigative leads are being pursued vigorously in an effort to identify possible suspect(s) and motives in the slayings," according to Wednesday's press release. People with information are asked to call the FBI's Rapid City office at 605-343-9632 or tribal police at 605-867-5513.

Organizers of last Saturday's "rally for justice" in honor of Black Elk and Hard Heart say family members have been frustrated in efforts to gain information, including specific autopsy results. The rally - which ended with the looting of a Whiteclay grocery store and claims of Sioux control over the town - also was meant to call attention to Whiteclay's heavy volume of beer sales to Indians from the reservation, where alcohol is banned.

Their frustration prompted a request Tuesday from new U.S. Civil Rights Commission member Elsie Meeks, an Oglala Sioux from rural Kyle, S.D., that her commission colleagues ask Attorney General Janet Reno to devote as many people as possible to the probe of the recent deaths.

Since the bodies were found, "there's been practically no information given," said Meeks, who put the request in a Tuesday letter to commission Chairwoman Mary Frances Berry. "It may be that there is no information, but it makes people feel that not everything has been told."

But tribal police and the FBI say people shouldn't be surprised when law enforcement is keeping information to itself. They say they have no evidence tying law officers to the deaths, but add that they can't risk divulging most of what they know about the fate of Black Elk and Hard Heart.

"Any time you release information that becomes known to the public, then the individuals who might be witnesses or suspects themselves become aware of that information," said Mark Vukelich, supervisor of special agents for the FBI's Rapid City office. He stressed that his comments reflected general rules of thumb about criminal investigations and weren't specifically related to the current probe.

If sensitive information gets out, several things can happen to damage the investigation, Vukelich said. People being interviewed can repeat the known information, making it hard to determine whether they knew the information on their own. If police tell about evidence they've found, that allows suspects or accomplices to destroy it.

"Once you tell one person, you lose control of where you send the information," he said.

Robert "Joe" Herman, acting executive director of the tribal police, said he knows what it means to be in the two families' shoes. His nephew was killed by a gunshot wound to the head a few years ago, he said.

"We were asking questions I knew investigators couldn't answer," Herman said. "It helps produce a lot of suspicion and a lot of distrust, but it's something we can't do without jeopardizing our investigation."

When asked last week if an explanation such as that made sense, rally organizer Tom Poor Bear said, "I could understand that, yes." But it doesn't make it any easier to live with the lack of information into the deaths, said Poor Bear, a half-brother of Black Elk and a cousin of Hard Heart.

The Sheridan County Sheriff's Office was first to respond when the two men's bodies were found. It handed off the case when it was determined that the bodies were on reservation land in South Dakota.

World-Herald staff writer Nancy Hicks contributed to this report.