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The Los Angeles County Department of Public Health reported 16 additional cases of the novel coronavirus on Sunday, bringing the total in the nation’s most populous county to 69.

The continued spread of the virus resulted in the decision to close all county building’s to the public, effective Monday, officials said.

The source of exposure for one of the new cases has not been identified, the agency said.

Three patients were exposed after recent travel, two are health care workers and four had close contact with a confirmed patient, according to the county health department. Five cases need further investigation, while the last case was reported by the Long Beach Health Department late Saturday, L.A. County officials said.

Long Beach city officials described that last patient as a woman in her 60s who was hospitalized in stable condition. The woman did not have a known exposure to a person who has COVID-19, and she did not travel to a place with known community transmission, authorities said.

Among the recently detected cases was a person who had been to West Covina High School, the West Covina Unified School District said Sunday in a statement. The district did not specify the person’s connection to the school.

“The individual is resting well at home under quarantine and is awaiting direction from the Department of Public Health regarding the notification procedures to others who have been exposed,” according to the WCUSD statement.

In the meantime, the district transitioned from dismissal to closure status at all schools, “effective immediately.” Students were barred from being on school campuses for any reason.

Voluntary remote learning was being offered through the district, although the work will not count toward students’ grade point averages.

“During this time of School Closure, all student work is optional and shall NOT be used to determine/affect grades,” the WCUSD statement added.

Local health officials and others across the U.S. have said that they anticipate more confirmed cases as more people are tested.

Later Sunday, Gov. Gavin Newsom called for the closure of all bars and wineries, as well as for people over the age of 65 and those with chronic health conditions to isolate themselves at home.

And Los Angeles County officials announced late Sunday that all county buildings would be off-limits to the public beginning Monday.

“We need to do all we can to protect the public and our employees in the midst of this expanding public health crisis,” Supervisor Kathryn Barger said in a written statement. “Our departments will continue to provide essential services to our residents, but it is prudent to limit public access to our facilities at this time. We will continue to monitor the situation and urge the public to follow the guidance of the Los Angeles County Department of Public Health.”