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.