Police in Manchester are appealing for witnesses after an arson attack on a warehouse being used for an illegal rave.

The ravers were enjoying an-night event on the ground floor of Hanover Mills, Ardwick, Manchester, when a fire broke out on the sixth floor just after 0530 GMT on Sunday.

Officers from Greater Manchester Police had been made aware of the rave at 0300 GMT, but chose to allow it to continue to avoid the risk of public disorder.

Most party-goers had left the former textile mill safely by the time crews from Greater Manchester Fire Service arrived.

Evidence of arson

The fire had spread from the sixth floor to the floors above and below.

More than 100 firefighters attended.

There were no serious casualties.

A spokesman for Greater Manchester police said: "You are damned if you do and damned if you don't in these situations.

"We were made aware of an illegal rave at around 0300 GMT and our officers went to assess the situation.

"They assessed it as a low risk and formed the opinion that it would be wiser to let it go ahead rather than risk public disorder if they tried to break it up."

Detectives said on Monday they had found evidence that a number of fires had been deliberately started on different floors of the building.