Washington, Sep 2 (DPA) Police were negotiating with a gunman who took an unconfirmed number of people hostage Wednesday inside the Discovery Channel headquarters in Silver Springs, Maryland, just outside Washington.

The man was identified as James Lee, an environmental protester critical of the TV network, CNN reported.

Lee reportedly entered the building wearing what appeared to be metal canisters on his front and back, and pulled out a handgun. Montgomery County police chief Thomas Manger said he couldn't confirm whether shots were fired inside the building.

The gunman was on the first floor of the building, in which 1,900 employees work. The building also houses a daycare centre, which was evacuated. Police said all the children were safe and with their parents.

Manger said, 'We believe most of them (employees) are out. There are a small number of hostages with him.'

An email sent to employees and read over the public address system read: 'We have reason to believe there is an armed gunman at One Discovery Place. All employees should seek protection in a locked office on their respective floors immediately.'

Lee reportedly posted a lengthy statement on a website called SaveThePlanetProtest.com, demanding that Discovery 'stop encouraging the birth of any more parasitic human infants.'

'Humans are the most destructive, filthy, pollutive creatures around and are wrecking what's left of the planet with their false morals and breeding culture,' the statement said, according to CNN.