The keepers of Thomas Jefferson's Monticello plantation announced yesterday that they have concluded that he probably fathered at least one and "perhaps all" of his slave Sally Hemings's six children, and they said they will include that information in tours and programs at the historic hilltop estate.

The announcement by the Thomas Jefferson Memorial Foundation, which owns Monticello, is based on the findings of a staff committee the foundation set up more than a year ago after genetic tests showed that America's third president very probably fathered Hemings's youngest son, Eston.

Until yesterday, the foundation had resisted taking a formal position on the hotly debated Jefferson-Hemings relationship and on the DNA study, which was conducted by a team of researchers led by retired pathologist Eugene Foster and released in October 1998.

When tourists at Monticello, some holding newspaper clippings on Foster's study, would ask about the long-rumored affair between slave and president, guides would answer the questions but offer no conclusions.

"We were basically agnostic going into this report," said foundation president Daniel P. Jordan, referring to the report issued yesterday by a committee of historians and other scholars. "Now we're taking a much stronger position. This is a milestone for us."

Jordan said the foundation will set up another panel to decide how to present the information about Jefferson's likely paternity in literature and programs at the estate, just southeast of Charlottesville.

Hemings descendants were buoyed by the foundation's new position.

"It's wonderful vindication," said Dorothy Westerinen, 42, of Staten Island, N.Y., whose family is descended from Eston Hemings. "To have the most professional historians, who have dedicated their lives to studying Thomas Jefferson, validate our claim is outstanding. We're thrilled."

Foster's team conducted DNA tests that compared the Y chromosome in males who trace their ancestors to the Jefferson family with that of male descendants of Hemings. The tests showed a match between the descendants of Eston Hemings and a male line of Jeffersons. Those results, combined with historical evidence, all but confirmed a liaison between Jefferson and Hemings, the researchers said.

The finding rocked historians, many of whom had largely dismissed allegations that the author of the Declaration of Independence consorted with a slave. Many Jefferson descendants continue to argue that the DNA results are not conclusive and that one of several Jefferson males could have fathered Hemings's children.

But the report released yesterday by the foundation said all the evidence strongly suggests that Thomas Jefferson was the children's father. One of the strongest pieces of evidence, according to the report, is that the dates when Hemings conceived her children match the dates of Jefferson's stays at Monticello.

Dianne Swann-Wright, director of special programs at Monticello and chairman of the committee, said historians will never know whether Jefferson and Hemings had a relationship based on friendship, love or force. But she said the evidence that Hemings and her family were given special treatment at Monticello is incontrovertible.

"We have no idea what she said to him or what he said to her," Swann-Wright said. "But what we do know is that each of her children who lived to adulthood lived out their lives as free people, and they were the only African American family, nuclear family, at Monticello to do that."

Hemings's descendants have long regarded their link to Jefferson as fact based on oral histories passed down from previous generations. In May, a small group of Hemings descendants were invited for the first time to attend the annual meeting of the Monticello Association, a group of 700 descendants who trace their lineage to one of Thomas Jefferson's two daughters. Membership in the all-white association is exclusive to those who can prove they are descendants of Jefferson and carries the privilege of burial at the Monticello graveyard.

The May meeting was largely contentious, with members of the association voting only to approve a panel to study the DNA results and its potential effect on new membership in the group. That panel has yet to issue any findings.

James Truscott, the association's president, said yesterday he is "very happy" to have the foundation's report and will consider it alongside his group's own research.

His nephew Lucian K. Truscott, a member of the association and outspoken critic of the group for not automatically admitting the Hemings descendants, said the Monticello report will put needed pressure on the association.

"This report is the emancipation proclamation for the Hemingses," Lucian Truscott said. "It sets them free from 200 years of denial and refusal in the minds of Americans, but they've been free all that time anyway in their own minds."