SAN JOSE (CBS SF) — Health authorities in Santa Clara County have identified multiple new cases of COVID-19 among construction workers in the county, prompting several sites to close down operations.

The county health department said the cases identified this week among construction workers include those at four construction sites in the county, with the largest outbreak at a site in Mountain View where 10 cases were confirmed and more than 30 potential exposures.

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The construction company operating the site proactively notified the health department once the first case was discovered and has voluntarily closed at the request of the county until further notice.

Under the current health order for Santa Clara County, construction activities have been allowed since May 4 but with strict safety and social distancing protocols specific to the industry.

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“These cases emphasize the fact that we are still in the midst of a pandemic,” said County Health Officer Dr. Sara Cody in a prepared statement. “With additional sectors reopening, it is vital that everyone carefully follow social distancing protocols to ensure that workers are safe. This includes keeping physical distance and wearing a face covering.”

Three other construction sites, two in San Jose and one in Milpitas, each reported between three and five cases and have also closed down at the request of the county health department. Nine other construction sites in the county have had at least one confirmed case, and health officials are working with the operators of those sites to determine if there are any more infections.

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The health department said it was working with construction trade and labor organizations to educate them on current protocols and to make sure information on coronavirus prevention practices is being disseminated among workers.