Twelve search warrants were executed in Hamilton, Peel and Toronto early Thursday, Const. Wendy Drummond of Toronto police told CBC Hamilton.
The organized crime and guns and gangs unit arrested several people, she said.
"We're in the process of going through the seizures and laying charges," Drummond said. She couldn't yet say how many people were arrested in Hamilton, where, or what was seized.
More information would likely be coming later Thursday, she said.
Const. Debbie McGreal-Dinning, a spokesperson for the Hamilton Police Service, said on Thursday that arrests had been made and Hamilton officers were involved, but that was all she knew.
Toronto police conducted a series of early-morning raids in the city's east end Thursday.
One of the raids took place in a townhouse complex (near Morningside and Old Finch Avenues) where a man and a woman were taken into custody.
Some residents say they were sleeping at 5:30 a.m. when they heard a loud bang and then the sounds of people yelling.
The townhouse was one of at least five addresses raided in the Toronto area.