Fourteen people are being quizzed after a series of police drugs raids across Wigan earlier today.
Detectives swooped on a number of homes in the borough and Merseyside as part of Operation Land, a probe into drugs networks.
And organised crime officers say a "substantial" amount of hard drugs has been seized as a result.
Ten men and four women are currently in custody awaiting questioning as a result of the inquiry.
Supt Steve Keeley, of GMP’s Wigan borough, said: “Drug abuse, addiction and supply have a devastating effect on individuals, those close to them and on the communities they live in.
“We tirelessly investigate people who benefit from the supply of drugs and work with partner agencies to offer the help and assistance needed by those impacted by these substances.
“Our aim is always to protect communities and work together in doing so, which is why I’d ask the public to continue to report anything suspicious to police.”
Those arrested are said to be aged between 19 and 51 and all were detained on suspicion of supplying class A drugs.
Anyone with information about the drugs trade should contact police on 101 or the Crimestoppers hotline, in confidence, on 0800 555 111.