CS gas used in London siege

Water is being sprayed through the flat's windows

Police have fired CS gas into a building where a gunman has been under siege since Boxing Day.

The police action followed an earlier exchange of shots between gunman Eli Hall and armed officers.

Part of the building in Hackney, east London, has been on fire, and the gas was aimed into an area where they believe Mr Hall, 32, is hiding.

Officers resorted to CS rounds in an attempt to force an end to the UK's longest armed siege.

We are evaluating the structure of the building because there are real fears that it's structurally unsound

Commander Bob Quick, Metropolitan Police

Six small explosions were heard at the building on Thursday evening.

A BBC reporter at the scene said there was a burst of activity around the flat in Hackney and a man had been heard shouting.

Earlier, officers had to shoot plastic baton rounds to smash the windows of the flat to enable firefighters to douse flames with water.

About 43 people have been trapped inside their homes near the scene and the incident has caused massive disruption to the area.

Police fear Mr Hall may have hardened his attitude to the idea of coming out peacefully.

Smoke inhaled

After the shots were fired, police negotiators used loudhailers to plead with the gunman to give himself up immediately.

He is known to have petrol inside and police believe he started the fire himself.

Metropolitan Police Commander Bob Quick said the gunman would have inhaled a considerable amount of smoke and police have not heard from him since the fire broke out.

"There are parts of the building relatively unaffected by the fire so the gunman could have sought refuge there and be alive and well.

"However we have no information on his well-being at the moment and we are evaluating the structure of the building because there are real fears that it's structurally unsound."

Earlier Scotland Yard said it was still committed to ending the siege peacefully.

Hostage escapes

The operation began when officers were fired on as they tried to remove a car for forensic tests.

Shots were fired twice on Sunday and again on Monday night.

Four streets around the area are closed and about 50 police officers are deployed around the clock.

Another man was held hostage for the first 11 days of the stand-off, but the man, who has not been named, managed to escape on Sunday.