Updated

Police have arrested a man who took several hostages at the New Hampshire campaign office of Sen. Hillary Clinton.

The siege appeared to have been resolved peacefully Friday evening, when authorities took the suspect into custody about 6:15 p.m. EST. The people he held captive were released unharmed one by one throughout the afternoon and evening.

Authorities said Friday that the suspect was Leeland Eisenberg, who has a number of aliases. He walked into Clinton's Rochester, N.H., office claiming to have an explosive device strapped to his body, and held at least four people hostage for more than five hours.

Clinton, who was not in New Hampshire Friday, planned to make a statement about 7 p.m. EST.

The suspect was described as in his 40s with salt-and-pepper hair, according to Foster's Daily Democrat, a local newspaper. Eisenberg has a history of mental illness and reportedly told his stepson to watch the news on Friday, the paper reported.

The suspect released two hostages he was holding earlier Friday afternoon, law enforcement officials told FOX News.

A woman believed to be a third hostage emerged about 5:30 p.m. and another woman thought to be a fourth hostage was freed about 6:15 p.m. About the same time, police arrested the assailant and took him away in a tactical vehicle.

Those who were let go earlier Friday — believed to be staffers — included a woman with a child.

There were no reported injuries, Callaghan said earlier Friday afternoon at a news conference.

The drama began to unfold just after 1 p.m. Friday when a distraught man walked into the campaign office saying he wanted to speak with Clinton.

The man ordered people onto the floor and then let a mother and her baby leave, said State Police Maj. Michael Hambrook. Two of the hostages he kept were volunteers, according to Bill Shaheen, a top state campaign official.

Witnesses reported that the assailant had flares, not a bomb as he claimed, strapped to his body. Federal law enforcement officials monitoring the situation from Washington confirmed to FOX that the suspect had flares in his possession that were purchased earlier at a local hardware store.

Three agents and a supervisor with the Bureau of Alcohol, Tobacco and Firearms arrived in Rochester Friday afternoon to help, a federal source told FOX News. One of the agents assisted New Hampshire state officials in negotiating with the suspect, according to the source.

The FBI and the Secret Service, as well as multiple local police forces and agencies, were also on hand, Callaghan said.

Police and SWAT teams used loudspeakers to communicate with the man.

"There is an ongoing situation in our Rochester, N.H., office. We are in close contact with state and local authorities and are acting at their direction. We will release additional details as appropriate," the Clinton campaign said in a release issued at about 2:45 p.m. EDT.

Clinton canceled a scheduled speech Friday afternoon at the Democratic National Committee fall meeting in Northern Virginia, party chair Howard Dean announced.

Clinton was said to be monitoring the situation from her Washington, D.C., home. Husband Bill Clinton has a scheduled event in Newton, Iowa, where he was campaigning for his wife.

Sharpshooters were positioned near the building, and at least one tactical bomb-squad unit was also on the scene. A nearby elementary school was in lockdown, and later evacuated.

Other nearby presidential campaign offices were also evacuated, including those for Sen. Barack Obama, D-Ill., and John Edwards, as well as several area businesses, according to news reports.

Callaghan characterized the incident earlier Friday afternoon as a "hostage situation" that was under control, but said the investigation was ongoing.

"The situation is still fluid," Callaghan told reporters. "I want our residents to know that the area is stabilized and we’re very confident we have the resources available to handle this situation effectively and safely. ... We have a secure perimeter of about four to five blocks."

He declined to offer any more specifics about the case, the suspect or the hostages.

"It's inappropriate to do that right now," he said.

Witness Lettie Tzizik said she spoke to a woman shortly after she was released from the office by the suspect, according to WMUR in Manchester, N.H. The woman was carrying an infant and crying.

"She said, 'You need to call 911. A man has just walked into the Clinton office, opened his coat and showed us a bomb strapped to his chest with duct tape,'" Tzizik quoted the hostage as saying.

The small Clinton office is located in the New England community's downtown area in a strip of several storefronts, and has large glass windows with a campaign sign out front.

The incident is not a first for a presidential campaign, though such occurrences are extremely rare.

In March 1980, intruders claiming to be with the Puerto Rican separatist organization Armed Forces of National Liberation (Fuerzas Armadas de Liberacion Nacional, or FALN) stormed the campaign offices of Jimmy Carter in Chicago and George H.W. Bush in New York.

They bound and gagged campaign workers in both offices, but left without injuring anyone after spray-painting nationalist slogans on the walls.

There have also been several non-fatal explosions at the campaign offices of other politicians, none of whom were running for president.

In June 2003, a pipe bomb filled with roofing nails exploded outside Calif. Rep. Loretta Sanchez’s campaign office in Santa Ana, Calif. Garden Grove resident Hai Duc Le, who was severely scarred in the incident, was sentenced to 21 months in prison for the blast. No one else was hurt, and authorities said at the time that the congresswoman was not a target.

In 1998, a soda-bottle bomb blew up outside Jesse Ventura’s gubernatorial campaign office in Minneapolis. Again police said they didn’t think the bombings were politically motivated, and no one was hurt.

And in 1994, then-Wisconsin Gov. Tommy Thompson’s campaign office was also struck by a pipe bomb, but no one was wounded.

FOX News' Carl Cameron, Catherine Donaldson-Evans, Ian McCaleb, Catherine Herridge, Major Garrett and Judson Berger as well as The Associated Press contributed to this report.