Mark Potok, a senior fellow at the Southern Poverty Law Center, said Mr. Page had come to the center’s attention a decade ago because of his affiliation with rock bands known for lyrics that push far past the boundaries of tolerance.

“The music that comes from these bands is incredibly violent, and it talks about murdering Jews, black people, gay people and a whole host of other enemies,” Mr. Potok said. He added that in 2000, Mr. Page tried to buy unspecified goods from the National Alliance, which Mr. Potok described as a neo-Nazi organization that at the time was one of the country’s best organized and best financed hate groups.

But Mr. Potok said the center had not passed any information about Mr. Page to law enforcement.

“We were not looking at this guy as anything special until today,” he said. “He was one of thousands. We were just keeping an eye on him.”

Although little known among music fans, a steady subculture of racist and anti-Semitic rock bands has existed on the margins of punk and heavy metal in Europe and the United States since at least the 1970s. Hate groups sometimes use some of the bands and their record labels for fund-raising and recruiting, according to the law center and the Anti-Defamation League.

In an interview posted on the Web site of the record company Label56, Mr. Page mentioned going to Hammerfest, an annual white-supremacist festival well known to civil rights advocates. He also said he played in various neo-Nazi bands, including Blue Eyed Devils, whose song “White Victory” includes the lines: “Now I’ll fight for my race and nation/Sieg Heil!” The company removed the interview from its site on Monday.

Analysts for the F.B.I. and the Department of Homeland Security routinely monitor violent extremist Web sites of all kinds, including those attracting white supremacists, according to former officials of both agencies. But the department’s work on the topic has been criticized. In 2009, conservatives in Congress strongly objected to a department report titled “Rightwing Extremism,” which speculated that the recession and the election of a black president could increase the threat from white supremacists.