KITCHENER -- An outbreak at a congregate living setting at a southern Ontario fruit farm has grown to 40 cases.

Kevin Martin with Martin's Fruit Farm confirmed to CTV News on Monday that the outbreak is at Vienna Farms, one of the company's orchard facilities. He said farm officials learned about a positive test on Friday and tested everyone at the site.

He said that the cases were identified in migrant and local workers.

On Tuesday, Southwestern Public Health (SWPH) officials confirmed that the total number of cases connected to the farm had grown to 40.

A total of 157 swabs were processed, with the results of three still outstanding as of Tuesday afternoon.

"We believe that there has been a lapse in compliance with the public health measures that has resulted in the 40 cases," said Dr. Joyce Lock, medical officer of health with Southwestern Public Health.

Dr. Lock didn't elaborate on what that lapse was or who was responsible.

Martin's Family Farm said the bunkhouses range in size from two beds to 21.

"The close proximity to one another facilitated the quick spread of the virus throughout the group," Dr. Lock said.

One worker was undergoing treatment at a local hospital, while the rest were in self-isolation and "receiving support from their employer, Southwestern Public Health, and appropriate community services," a news release said in part.

"We're just concerned about health and safety," Martin told CTV Kitchener on Monday. "We're working very closely with public health and isolating any positive cases."

SWPH said that it had done an on-farm inspection and is working with Martin's Fruit Farm to prevent any future outbreaks.

The first case was identified on Friday and more than 150 people were tested by the end of Saturday.

Some workers said they went back to work that day before they received their results.

Kit Andres with the Migrant Workers Alliance for Change, said some workers felt "forced" to return to the field.

"Workers are worries, even the ones who tested negative," Andres said. "They are thinking well I went back to work right next to people who tested positive, so maybe they have been infected since then."

Martin said it was his understanding that a return to work was allowed.

"At that point in time, there was only one positive test," he said. "I think it's fair to say we would have encouraged them to work, because it's outside, as we all know is a better situation than, say, inside."

He said safety is a top priority and the company is working with public health.

None of the company's other locations are impacted by the outbreak.

Anyone who tested positive is in isolation and contact tracing continues.

Mayor Ed Ketchabaw said Monday that the outbreak was unexpected, noting that Bayham, the community where the farm is located, had had low infection rates for the months before.

The outbreak represents a substantial portion of new cases reported in the area over recent days. Middlesex-London, for example, reported just one new case of COVID-19 on Monday, though Tuesday's case count rose to eight.