WATERLOO — Drug investigators in haz-mat suits seized "thousands of pills" during a drug raid Sunday on a home in the Beechwood neighbourhood of Waterloo.

About half a dozen officers were involved in the raid on the detached home at 173 Briarcliffe Cres. , said Staff Sgt. Sloden Lackovic of Waterloo Region Police. He said investigators had been on site since Sunday morning and would likely be there until early evening.

The officers seized "thousands of pills and equipment we believe is used to manufacture pills," Lackovic said.

The officers, who were wearing breathing apparatus and were fully covered with hooded suits, gloves and boots, removed piles of equipment and bagged material from the home, including a portable generator, a mechanical hopper and other equipment. Firefighters hosed officers down to remove any contaminants after they emerged from the house.

Lackovic wouldn't say what the suspected pills were, or provide an estimated street value.

"We won't know what the pills are until we get results from Health Canada," which is testing the seized pills, he said. "We don't have a value because we still have to determine what the pills are."

The raid is part on an ongoing, months-long drug investigation, Lackovic said. The raid came about after the arrest Saturday afternoon of three men and one woman, all in their 20s, and all residents of the Kitchener-Waterloo area, he said. The men were held in jail pending a bail hearing Monday, while the woman was released on a promise to appear in court Monday.

The four face numerous charges, he said, including manufacturing a controlled substance, possession of a controlled substance for the purpose of trafficking, possession of a controlled substance for the purpose of exporting, and possession of a prohibited weapon, which Lackovic said was a knife.

Neighbours said the house, a single detached home with pale-blue siding and rusty railings, has been empty for the last three or four years, but about two weeks ago a truck pulled up and people appeared to have moved in.