TORONTO -- Police in Halton region say they have seized the greatest haul of the deadly opioid fentanyl in its service's history, including cocaine and pills worth an estimated $4 million on the street.

Police said that starting in the fall of 2019, Halton Regional Police Service (HRPS) investigators started pursuing two individuals suspected of drug trafficking in Oakville.

Dubbed "Project Mover," the investigation took officers well beyond Oakville and into several other jurisdictions across the GTA.

Between June and September, a total of nine people were arrested.

Officers allegedly seized 10 kilograms of fentanyl, one kilogram of cocaine, MDMA, and six kilograms of an unknown drug they have yet to identify.

They also seized a semi-automatic shotgun, a .40 calibre handgun with an extended magazine and two vehicles – a 2019 Dodge Durango and a 2016 Acura RDX.

Deputy HRPS Chief Jeff Hill said the seizure of that amount of fentanyl could prevent the deaths of "five million people."

"As little as 2mg of fentanyl can kill a person," he said.

Charges laid included possession for the purpose of trafficking, possession of property obtained by crime and firearms offences.

All but one of the individuals was later released on a promise to appear.