A person who has sent threatening letters denouncing interracial relationships to some National Football League players and other prominent black men is now targeting high school athletes, authorities said Thursday.

St. Ignatius and St. Edward, two Roman Catholic high schools in Cleveland with well-known sports programs, received threatening letters addressed to student athletes, FBI special agent Bob Hawk said. St. Ignatius received eight letters Nov. 30. St. Edward’s received two letters last week.

Hawk said he only knew of schools in Ohio receiving letters.

Over the past two years, 60 such letters have been sent to at least six NFL players and other well-known black men across the nation, including civic and business leaders. None of the recipients has been identified.

The mail, postmarked from cities in northeast Ohio and Pennsylvania, criticized interracial relationships and direct the men to end such relationships “or they’re going to be castrated, shot or set on fire.”

The letters were usually signed “angry white woman” or “angry Caucasian woman.”

There is no suspect and the FBI is asking anyone with information to contact the agency. An offender could be charged with sending threats through the mail, which is punishable from six months to five years in prison.

“It’s hard to say what trips this guy’s switch. My guess is that he sees a photo in a newspaper or magazine or shown on TV — that’s speculation — where a black male is in the company of a white female, and I think that’s what trips his switch and the letters follow,” Hawk said.

The letters mailed to St. Ignatius were addressed to the soccer team and players for other sports — some from other area schools — who were photographed for a local newspaper’s scholastic sports section, said Carolyn Kovach, the school’s spokeswoman.

The black athletes were pictured with white, female athletes.

Kovach said the writer had apparently assumed the athletes were dating. “All I know is they appeared in photographs together,” she said. “It’s ridiculous. I want this person to know you’re creating alarm and hurting people with your words. I can’t believe people think this way in 2004.”

The mail was intercepted by school security and never made it into the hands of the students, whose parents were immediately notified. The school called the FBI and was unaware that it was part of a larger case, Kovach said.

St. Ignatius has toughened its security that includes cameras and guards. The students involved were given parking spaces closer to the school entrance and told that “at anytime if they want a security escort to their cars to let us know,” Kovach said.

St. Edward principal Eugene Boyer said his school received two letters “of a racist and threatening nature that we immediately turned over to the FBI.” No specific student was named in those letters, he said.