Police have arrested a man at the scene of the Tottenham Court Road bomb scare.
A man, who had been identified earlier by witnesses as Michael Green, 49, entered a building on the busy central London road with gas cylinders allegedly strapped to his chest and threatened to blow himself up just before midday.
Police are refusing to confirm the identity of the arrested man or the suspect.
He allegedly walked in to the offices of Advantage, an HGV driver training company, and was angry about a failed course he had taken on which he wanted a refund.
Around four hostages are thought to have been held captive and subsequently released after police negotiators made contact.
Electrical items and paper rained down on Tottenham Court Road from the windows of the fifth-floor office he was occupying.
Before the hostages were freed he is thought to have made them help him hurl items out of the window.
Snipers perched on nearby rooftops and armed police hovered around the lobby of Shropshire House at 179 Tottenham Court Road, the building in which Advantage's office sits.
Hundreds of office workers gathered on the streets below and were pushed back by a 300m cordon set up by police.
London Ambulance Service, who had several emergency vehicles on hand, confirmed that there were no reported injuries.
Warren Street and Goodge Street underground stations were forced to close because of the police cordon and cars were directed away from the area.
A video was uploaded to YouTube of one of the Advantage workers who was in the office when the siege started.
"What's happened is we were in the office, someone came in and we asked him what his name was. I recognised him because he was one of our previous customers," said Abby Baafi, 27, the head of training and operations at Advantage, in a video recorded by Stephen Hull, executive editor of the Huffington Post UK who was at the scene.
"He just turned up in gasoline cylinders. He threatened to blow up the offices. He said he doesn't care about his life, he doesn't care about anything, he's going to blow up everybody."
She said he was looking for her, but let her go because she said she was pregnant.