A Vancouver, Wash., frozen berry processing plant announced May 26 that 84 people, including 69 employees and 15 of their close contacts, had tested positive for the coronavirus in what has become one of the largest COVID-19 outbreaks at a food processing plant on the West Coast.

Firestone Pacific Foods shut down operations of its berry facility May 19, Clark County health officials said in a press release. Facilitywide testing began three days later, on May 22.

"These cases may have gone undetected and potentially exposed others had we not facilitated testing of all employees," Dr. Alan Melnick, Clark County health officer, said in a press release on Tuesday. "By being proactive, we have hopefully kept this outbreak contained to Firestone employees and close contacts, and prevented the outbreak from spreading into the community."

Washington state health officials have paused the reopening of Clark County, across the Columbia River from Portland, until the outbreak is contained. County health officials said they do not believe the outbreak has spread beyond Firestone employees or their close contacts.

So far, there are 510 known COVID-19 cases in Clark County, and 25 deaths that have been linked to the virus.

The Firestone Pacific outbreak ranks among the largest at a West Coast food processor. In Walla Walla, Wash., which also borders Oregon, nearly 250 workers at a Tyson processing plant have tested positive for the virus, the Seattle Times reported. And at the Farmer John meatpacking plant in Vernon, Calif., over 150 workers have been diagnosed with COVID-19, according to ABC News.