Suspects in a heroin supply network have been arrested in a series of early morning raids.

As five people were being questioned by detectives last night, it was revealed more arrests are to follow.

Detective Inspector Derek Carter, of Cleveland Police, said: "We are now in an initial arrest phase of our operations. We know there are other individuals linked with this group and they will face major disruptions to their activities very, very shortly.

"Our main tools in targeting organised crime are determination, patience and stealth, and operations we have in place to disrupt and dismantle crime gangs will continue for a long time to come."

Operation Grinstead - the codename for yesterday's swoop on homes and businesses in Stockton - involved 70 police offices, ranging from rapid response units and sniffer dogs to specialist financial investigators, and marked the culmination of months of planning by Cleveland's Organised Crime Unit.

Officers seized £5,000 in cash from one house, an imitation firearm and ammunition from another, steroids, cannabis and more than 400 blue tablets, which are being analysed.

They also seized computers, weighing scales and financial documents.

Det Insp Carter said: "This is just the start.

"We have been quietly gathering evidence for months against a number of individuals to allow the operation to go ahead.

"We know this is a gang who, from their Stockton base, have links throughout the North and deal in kilos of heroin. They are major players.''

The houses raided in Stockton were in Hartington Road, Richmond Road, Parliament Walk and Clarendon Road, in Thornaby.

Riverside Tyres, in Boathouse Lane, and an address in Dovecot Street were also targeted.

The raids were carried out under the Sabre banner - the anti-crime initiative launched by Cleveland Police just over a year ago, which has so far resulted in more than 1,300 arrests.

The five people arrested yesterday were all men, in their 20s and 30s.

Det Insp Carter said: "Part of our operation is to carefully examine the assets and wealth of the individuals we have arrested and look at the property they have to see if there are links to acquisitive crime."

Assets seized by the Organised Crime Unit, which are going through legal processes, total more than £1.2m.