BRADFORD, ONT. -- Migrant workers have emerged as yet another vulnerable group during the pandemic, with hundreds of workers becoming infected with COVID-19 while working on Canadian farms.

The province has tested more than 700 workers, Premier Doug Ford said at a news conference on Tuesday.

The Simcoe Muskoka District Health Unit (SMDHU) confirmed an outbreak at two local farms, but details remain confidential.

"It's our practice with outbreaks outside of health care to not provide the names of the businesses or premises involved unless it's necessary to do so to protect the public," explains Dr. Charles Gardner, SMDHU medical officer of health.

The health unit reported 12 confirmed cases in the two separate outbreaks locally. Three of those cases are in Bradford, where workers from Mexico and the Caribbean do much of the farm work.

Public health officials have visited the farms and tested dozens of workers.

Meanwhile, NDP Leader Andrea Horwath said she wouldn't blame migrant workers if they were wary of getting tested, given their precarious position.

"These folks are literally at risk of being deported if they are not able to provide the labour that they are supposed to be providing to the farm," she said. "So there has to be a guarantee put in place that they're not going to be deported and that their health and well-being is going to be looked after."

The government of Mexico recently expressed concern for worker's safety and considered stopping them from travelling here.

But Keith Currie, Ontario Federation of Agriculture president, says that has been averted.

"Assurances have been made that protocols are being followed, so these workers still have access to come into Canada and work on Ontario farms," says Currie.

The federation is now supporting a plan to do on-farm testing, so workers won't have to travel to be tested.

With files from The Canadian Press