Officers said a "huge recovery" of what were believed to be controlled substances were recovered in a pre-planned operation in Staffordshire.
Properties in Manchester, Essex and London are also being searched.
The suspects are currently in custody and being questioned on suspicion of conspiracy to supply Class A drugs.
They include four men from London, aged 25, 28, 29 and 56, a 45-year-old man from Northolt, two men from Poland, aged 32 and 48, and a 44-year-old man from the Netherlands.
The raids on Friday evening involved officers from the Titan North West Regional Crime Unit and the National Crime Agency.

Corran "Coz" Powell, 21, died following the collision in Braintree, Essex, in December 2014.
His family is raising money to buy a particular area of land on which he dreamed about running outdoor survival courses for disadvantaged young people.
The centre would also be used as a venue for new bands and charity events.
"I can't think of anything else we could have done that was more fitting, or more Coz," his mother Gennie said.
"I think he'd be 100% behind it. If he's watching now he'd be saying 'Come on Mum, keep going'.
Mrs Powell said even if they could not raise enough money to buy the land "he loved and built his plans around", his relatives would make sure they followed through "even if it's just three acres".
Mrs Powell said her son, who was from Gosfield, Essex, dreamt of "teaching other young people to understand, be safe in and respect our countryside".
"He loved being active outdoors and having been introduced to woodland survival was passionate about the skills and confidence it gave him," she said.
On the family's fundraising page, Mrs Powell wrote: "We have the skills and knowledge to set up the kind of Centre that Coz had in mind but we do not have the money."
The family will contribute money paid from Mr Powell's car insurance life cover towards its Â£200,000 target.

Police said the attackers entered the property on Craigmillar Castle Road at about 20:15 on Friday. Police believe the attack may have been targeted.
A 38-year-old man suffered serious, but non-life threatening, facial injuries and was taken to hospital for treatment.
The second victim, aged 49, did not need medical attention.
Det Insp Alan O'Brien. of Police Scotland, said: "We believe this may have been a targeted attack and are working to establish the full circumstances.
"I'd urge anyone who may have seen suspicious behaviour by three men in the area at this time to come forward.
"We're also eager to trace any suspicious vehicles seen in the street around this time, and I'd again ask anyone who may have information about this get in touch."
Eight men have been arrested on suspicion of drugs offences after three vehicles were stopped on the M6 motorway.
[NEXT_CONCEPT]
The family of a young musician killed in a car crash is aiming to fulfil his lifelong ambition to buy land and create an outdoor centre for children.
[NEXT_CONCEPT]
Two men have been assaulted by three masked attackers at an address in the Craigmillar area of Edinburgh.