FBI agents and civil rights division investigators also are looking into vandalism and other incidents at mosques or mosque construction sites in Arlington, Texas; Murfreesboro, Tenn.; Madera, Calif.; and Waterport, N.Y.
The open criminal investigations were confirmed by civil rights division spokeswoman Xochitl (SOH-chee) Hinojosa in response to a query from The Associated Press.
The suspected anti-Muslim incidents, following the uproar over a planned mosque near ground zero in New York and Saturday's planned burning of copies of the Quran at a church in Gainesville, Fla., were the topics of a meeting Tuesday between Attorney General Eric Holder and Muslim and other religious leaders.
Holder called the planned Quran burning, to coincide with the ninth anniversary of the Sept. 11 attacks, "idiotic and dangerous," the religious leaders said following the private meeting.
A Justice Department official who was present confirmed Holder said that the plan by the Rev. Terry Jones to burn copies of the Quran at his church was idiotic. But the official, who requested anonymity because the meeting was private, said Holder was quoting Gen. David Petraeus, the U.S. commander in Afghanistan, when he used the word "dangerous." Petraeus said the book burning could endanger U.S. troops.
Justice spokesman Matthew Miller said afterward that Holder "reiterated the department's strong commitment to prosecuting hate crimes, and noted several successes."
In the past 18 months, the department "has prosecuted three men who burned a mosque in Tennessee, two others who burned an African-American church in Massachusetts and another who spray-painted threats on a synagogue in Alabama, among other cases," Miller said. "Violence against individuals or institutions based on religious bias is intolerable and the department will bring anyone who commits such crimes to justice."
The religious leaders had sought a forceful public statement from Holder condemning hate crimes, and suggested he speak out before the Sept. 11 anniversary. They also want an order for his community relations service to try to defuse tensions over Jones' plans.
The White House and State Department also said Tuesday that the desecration of the Quran could endanger U.S. troops and civilians abroad. But Jones said he still intends to go ahead.
The incidents have followed sustained criticism of the planned mosque near the former site of the World Trade Center in lower Manhattan. Early plans for the project known as Park51 call for a 500-seat auditorium, a Sept. 11 memorial and prayer space.
Among the incidents under investigation as potential hate crimes, all dating from July and August:
• A Muslim cab driver in New York City had his face and throat slashed in a suspected hate crime. Michael Enright of Brewster, N.Y., has been indicted on state hate-crime charges in the attack and could also face assault and attempted murder charges.
• Arson at the site of a future mosque in Murfreesboro, where leaders of the local Islamic Center won permission in the spring to build a new mosque after outgrowing their rented space.
• A brick nearly smashed a window at the Madera Islamic Center in central California, where signs were left behind that read, "Wake up America, the enemy is here," and "No temple for the god of terrorism."
• A fire and graffiti at the Dar El-Eman Islamic Center in Arlington, Texas.
• Police arrested five teenagers after the son of one of the founders of a mosque in Waterport, N.Y., on Lake Ontario was sideswiped by a sport utility vehicle. One teen was charged with firing a shotgun in the air near the mosque a few days earlier.