University police, meanwhile, met with federal and state law enforcement agencies Thursday to coordinate the investigation of this week's incident, the sixth case of racist hate mail on the campus since September 1998. None of those cases has been solved yet, according to information from campus police.

"With this type of crime when there is so little evidence ... the only way someone is going to get caught is if people talk," said Gerald Evans, a member of the university's board of visitors who donated $1,000 to the reward fund.

"I think we need to get it [the incident] behind us quickly and the money will help us do that," said Evans, who is white.

Police would not discuss specifics of the letters except to say that they threatened bodily harm to their recipients: the Department of Afro-American Studies, the Black Student Union and the president of the Student Government Association, Juliana Njoku, who is black.

Police said a fourth letter has been discovered, but would not say who it was sent to. All four letters were received Tuesday.

The campus newspaper Wednesday published what it described as full and unedited copies of two of the letters, which were filled with racial slurs and threats to destroy their recipients.

Campus President Clayton Mote Jr. started the reward fund Tuesday with a pledge of $1,000 of his own money. The fund snowballed after that, with a $5,000 pledge coming from Prince George's County Executive Wayne Curry at a campus rally Wednesday against hate incidents.

Curry, who is black, was not available for comment Thursday. But other donors were eager to talk about the reasons behind their pledges.

"I felt very, very upset at the notion that an individual ... could attempt to poison the climate that has taken so long to develop," said Bill Destler, vice president of research on campus, touting the gains in diversity at the College Park campus.

"I felt I had to do something. I put my money where my mouth is," said Destler, who pledged $1,000 toward the reward.

University Board of Regents member Edwin Crawford also donated $1,000 because, he said, he "felt it was necessary to do something so that those responsible [for the incident] could get their just rewards.

"On Tuesday, the worst side of humanity came out and it won't be tolerated," Crawford said. "We're a higher education community and if we can't set a cultural standard of tolerance and fair play for these young people before they go out into the work force then we haven't succeeded as a board or a society."

In the meantime, campus police, with the help of Maryland State Police, said they plan to boost uniformed patrols, particularly in areas frequented by minority students and organizations.