Police in British Columbia's Lower Mainland say a yearslong drug-trafficking investigation has led to charges against eight people, as well as the seizure of illicit drugs, drug-making supplies, and two guns with prohibited magazines.

A statement from B.C.'s Combined Forces Special Enforcement Unit says the investigation began in Langley in December 2022 and expanded as investigators determined the suspects were connected to "gang and organized crime activity."

Police say the probe led to the execution of 10 search warrants in Richmond, Coquitlam, Surrey and Langley between April and May last year.

They say the operation turned up "significant" quantities of illicit drugs and led to eight arrests, with federal prosecutors approving a total of 31 charges this week.

The accused are five men and three women ranging in age from 21 to 31, with charges that include trafficking a controlled substance for a criminal organization and possession of a restricted firearm without a licence.

Police say a 31-year-old man was being held in custody and the other seven accused have been released ahead of a provincial court hearing on Aug. 14.

The search warrants led to the seizure of 8.5 kilograms of the potent opioid fentanyl, 15 kilograms of the drug MDMA and one kilogram of cocaine, police say.

Officers also seized more than 4,600 pills including oxycodone, hydromorphone, fentanyl, and over 1,000 kilograms of chemicals used to make MDMA and fentanyl.