Enlarge Handout via AP The Tucson, congressional office of Rep. Gabrielle Giffords was vandalized a few hours after the House vote overhauling the nation's health care system, authorities said Monday.

WASHINGTON  The FBI is investigating acts of vandalism and a death threat aimed at Democrats who voted for the health care legislation.

A freshman Democrat from Virginia reported that a gas line had been severed at his brother's home, and two congresswomen — one in New York and another in Arizona — said windows at their district offices were smashed.

"A significant number, meaning more than 10" members received threats, said Majority Leader Steny Hoyer of Maryland, and officials from the FBI and U.S. Capitol Police talked with House Democrats Wednesday about how to protect themselves. Hoyer and other Democrats said the incidents may have been the work of angry opponents of the health care legislation, which President Obama signed Tuesday.

Rep. Louise Slaughter, D-N.Y., who on Wednesday disclosed two "alarming" incidents that occurred last week, blamed Republican leadership for "fanning the flames."

House Minority Leader John Boehner of Ohio condemned such misconduct. "Violence and threats are unacceptable," Boehner said Wednesday on Fox News. "Yes, I know there is anger, but let's take that anger, and go out and register people to vote, go volunteer on a political campaign."

The FBI is "seeking to identify those responsible" for threats against members of Congress, spokeswoman Katherine Schweit said Wednesday. She did not know how many threats had been made.

"Anybody who has information, we want them to contact us," Schweit said.

Slaughter, who had a prominent role in passing the historic legislation as chairwoman of the House Rules Committee, said a window in a district office was shattered by a brick and a voicemail "referencing snipers" was left on a campaign office phone. She said the FBI, Capitol Police and local authorities are investigating.

Rep. Tom Perriello, D-Va., said the FBI and local authorities are investigating the incident at his brother's house.

Perriello, who defeated Republican Virgil Goode by fewer than 800 votes in 2008, has been a target of conservative ire because of his vote for health care. Earlier this week, a "Tea Party" activist posted Perriello's brother's address on a blog, mistakenly identifying it as the congressman's home and urging readers to "drop by ... and express their thanks regarding his vote for health care."

"While it is too early to say anything definitive regarding political motivations behind this act," Perriello said in a statement Wednesday, "it's never too early for political leaders to condemn threats of violence, particularly as threats to other members of Congress and their children escalate."

Mike Troxel, the blogger who posted the Perriello address, could not be reached for comment Wednesday and his website was inaccessible. Troxel is a "participant" in a Tea Party group in Lynchburg, Va., said Mark Lloyd, the group's chairman. Tea Party members are conservatives who oppose increased government spending and regulations.

Lloyd said in an e-mailed statement that his group does not "encourage violence, damage to property, or criminal activity of any sort." He added: "If bad taste and poor judgment were a crime, then most of Congress would be behind bars."

In Arizona early Monday morning — shortly after the health care bill passed the House — vandals smashed the glass door at the Tucson office of Rep. Gabrielle Giffords, D-Ariz., her office said.

Giffords' spokesman, C.J. Karamargin, said a security guard reported the incident hours after he and others had left the office after watching the health care vote on television. Giffords voted for the legislation.

"That was the frightening thing, that people were here just before this happened," Karamargin said in a telephone interview from the Tucson office. "We feel lucky no one was injured."

He said the office had received many phone calls with "nasty and rude and hateful comments" from opponents of the health care bill.

President Obama believes that "people should have a right to ... passionate views," White House spokesman Robert Gibbs said. However, Gibbs said, people should "exercise those views not in a way that threatens anybody's safety or security, not in any way that foments violence."