The Avon and Somerset force is investigating the transfer of the cash from the city to the West Indies.

Officers say it represents up to 700,000 crack cocaine deals.

Fifty officers were involved in the raids, codenamed Operation Atrium.

'Substantial sum'

Eight people were arrested and about £100,000 recovered in the raids on Monday morning.

Detective chief inspector Bruce Ballagher of Avon and Somerset Police said: "We're investigating the transfer of just over £7m back to Jamaica through a number of premises.

"We believe that some of this substantial sum is connected with drugs money out on the streets of Bristol as a direct result of dealing in crack cocaine.

"It is quite clear that this is a predominant method that the drugs dealers are using to launder their money and it's part of our investigation to clamp down on that.

"So not only are we trying to stop the drugs reaching Bristol in the first place and arresting the dealers when they come here, but we are also going to disrupt their finances and take their money from them."

Detectives say they now have to unravel the laundering process.

Their intelligence during the four-month operation suggests huge amounts of money have been transferred from Bristol to Jamaica.

Drug dealing has become a big problem in some parts of Bristol with dealers working overtly on the streets.