A man with a bomb strapped to his chest has taken staffers in Sen. Hillary Clinton's New Hampshire campaign office hostage, a federal government official has confirmed.
Mrs. Clinton was in not in the Rochester area but in Washington, D.C., when the incident occurred around 1 p.m., the official said.
"Right now it is a state and local police effort," the official said. However, federal bomb experts could be called to the scene.
Area schools have been locked down, and one child and an adult have been released.
Two hostages remain, and police are setting up hostage negotiations.
Witnesses describe the hostage-taker as a man in his 40s with gray hair.
An FBI spokesman said the Rochester police and New Hampshire State Police have responded to the incident. "We are ready to assist if asked but we have not been asked," the spokesman said.
The Secret Service is also on standby to assist.
A hostage negotiator is trying to establish contact with the assailant, who reportedly has asked to speak with Mrs. Clinton.
She and other presidential hopefuls were preparing to speak at the Democratic National Committee's fall members meeting in Vienna, Virginia.
Audience members were awaiting afternoon speeches inside the ballroom from Mrs. Clinton, Rep. Dennis Kucinich of Ohio and Sen. Joseph R. Biden Jr. of Delware.
DNC Chairman Howard Dean announced she would not speak here today and described the hostage situation. Her supporters, who wore "Hillary" T-shirts, stickers and buttons, had packed the ballroom and were ready with signs. The crowd loudly gasped at Mr. Dean's words.
"Details are sketchy," Mr. Dean told disappointed members. "Senator Clinton is now dealing with a very difficult problem ... We will keep them in our prayers."
Mr. Kucinich also sent his best in his own speech.
"We're in solidarity with Hillary in this moment when we think of what she's going through and what her staff's going through," he said, to applause.
He went on to lament a society that has people who can only express themselves violently.
Mr. Biden gave his warm wishes to Mrs. Clinton as well.
"I pray to God that it all works out right and I wish Hillary the best of luck as she heads to new Hampshire," he said, though there is no indication she will be heading to the state.
The Clinton campaign released this statement: "There is an ongoing situation in our Rochester, NH office. We are in close contact with state and local authorities and are acting at their direction. We will release additional details as appropriate."
As the DNC meeting closed with a prayer for the "safe release of the Clinton campaign staff members," Clinton spokesman Guy Cecil worked the crowd, apologizing to supporters as they streamed out of the ballroom. Mr. Cecil refused to answer reporters' questions, including the wherabouts of the Mrs. Clinton and whether she would cancel her campaign trips.
Former President Bill Clinton is scheduled to campaign for his wife in Iowa tomorrow.
Clinton staffers in Iowa worriedly followed the situation via the Internet and streaming television. An Obama campaign office near the situation was evacuated as a precaution, according to news reports.