Four people have been hospitalised and 20 staff and patients evacuated from Queen Mary's Hospital, after a suspected arson attack early this morning (Saturday).

Eight fire engines and 58 firefighters attended the blaze, which started just after midnight on the first floor of a four-storey building at the Roehampton Lane hospital.

Firefighters wearing breathing apparatus rescued four female patients and a male member of staff, who were all taken to another hospital with smoke inhalation.

A total of 20 people were evacuated from the building, with 15 patients being transferred to Springfield University Hospital in Tooting.

The fire started in the 17-bedroom Rose ward, which is used by mental health patients.

The flames were brought under control just after 1pm. One bedroom was destroyed.

Winston Douglas, green watch manager at Wandsworth fire station, was one of the first at the fire.

He said: "Wandsworth, Fulham, Richmond and Hammersmith were the first crews to arrive, before stations from the surrounding area also attended.

"It was a really challenging job and the boys worked really really hard."

A Met Police spokesman said the fire was being treated as arson.

He said: "There has been no arrest, and nor was anyone detained by police regarding the incident.

"However it is expected that an 18 year old woman patient will be interviewed in due course regarding the inquiry."

A spokesman for South West London and St George's Mental Health Trust said: "Our immediate concern was for the safety of our staff and patients.

"Four patients and a male member of staff went to hospital with smoke inhalation. The staff member and three of the patients remained in hospital over night and are being discharged this morning.

"The ward has now been secured and we will cooperate fully with the police during their investigation."