Three hostages were able to escape safely, police told reporters just after 5:00 p.m.
The following is AP's previous story, it will be updated shortly
A man upset with the Discovery Channel's environmental programming took several people hostage at gunpoint at the company's headquarters Wednesday while wearing canisters strapped to his body, officials said.
Police were negotiating by phone with the gunman, who burst into the suburban Washington building about 1 p.m. waving a handgun.
The gunman took what Montgomery County Police Chief Thomas Manger described as a "small number of hostages" but he did not say how many. He also did not say what the man wanted or whether anyone was hurt. Police had not confirmed whether the canisters were explosives.
Manger said most of the 1,900 people who work in the building were able to get out safely.
A law enforcement official speaking on condition of anonymity because the investigation was ongoing said authorities have identified James J. Lee as the likely suspect.
A different official, who spoke on condition of anonymity for the same reason, said Lee previously protested outside the building, where he was arrested and charged with disorderly conduct in February 2008, according to court records.
Police reports indicate he paid homeless people to join his protest and carry signs outside the building. He gave one individual $1,000 for what he considered a prize winning essay.
At one point, a crowd of more than 100 people gathered around Lee, 43, who referred to money as "just trash" and began throwing fistfuls of it into the air.
At the trial, The Gazette of Montgomery County reported, he said he began working to save the planet after being laid off from his job in San Diego. He said he was inspired by "Ishmael," a novel by environmentalist Daniel Quinn and by former Vice President Al Gore's documentary "An Inconvenient Truth."
A website registered to Lee criticized Discovery and announced plans for the protest in January 2008: "These guys have been very sneaky and deceptive as to their contribution to the planetary problems. Just look at their 'new' show about saving the planet, 'Planet Green,' to me, it's just another show about more PRODUCTS to make MONEY, not about actual solutions. We can't let them get away with doing it anymore."
Discovery Communications Inc. operates cable and satellite networks in the U.S., including The Discovery Channel, TLC and Animal Planet. Discovery shows include "Cash Cab" and "Man vs. Wild," and TLC airs "American Chopper" and "Kate Plus Eight."
Animal Planet also airs the controversial series "Whale Wars," about attempts by environmentalists to disrupt the Japanese whaling industry.
After Lee's arrest, a magistrate ordered a doctor's evaluation, but court records do not immediately indicate the result. Lee was convicted by a jury and served two weeks in jail. He was also ordered to stay 500 feet away from Discovery headquarters.
Manger said most people made it out of the building safely Wednesday, though some might have still been stuck on the top floors.
Adam Dolan, a sales director in Discovery's education division, told The Associated Press by phone that he was heading to lunch with a co-worker when he heard there was a situation in the building.
He was told to go back up to the top floor, lock the door and turn off the lights. Eventually the workers were herded down a stairwell and told to go home.
"Everyone was very scared, but at the same time ... I think people were calm and collected and responded as one would expect in this situation," said Dolan, 28.
When he got to the bottom floor, he saw shattered glass near the company's daycare and suspected it was broken to get the children out. He later got an e-mail that all the children were safe and had been taken to a McDonald's.
Dolan said the company has unarmed security guards who won't let anyone into the building without a badge.
Melissa Shepard, 32, of Peterborough, N.H., a consultant who works there during the week, said she was on the third floor in a large room with several other workers when someone announced over a loudspeaker that there was a situation in the lobby and people should stay at their desks.
After some time, they were told to move to the other end of the building. She said she was among a dozen workers who huddled into an office, shut the door and turned off the lights.
Then she said someone knocked on the door and told them to leave the building. She said there was some confusion as they were told to go to an upper floor or down the stairs.
"Finally, I screamed, 'tell us where we need to go...I just want to get out of there,"' she said. "I was shaking...I was like what do we do what do we do?"'
Authorities descended on the area, and people were being kept away from the main drag of the downtown area where the building is located amid restaurants and shops. Traffic was jammed.
Associated Press Writers Kathleen Miller in Silver Spring; Matt Apuzzo, Eileen Sullivan and Nafeesa Syeed in Washington; Ben Nuckols in Baltimore; and Jacob Jordan in Atlanta contributed to this report.