Lansing — Michigan confirmed Thursday night that 10 new individuals have tested positive for coronavirus, bringing the "rapidly evolving" statewide total to 12 and triggering the closure of the state's K-12 schools.

The new cases tested in the state's Lansing lab are spread among Ingham, Kent, Montcalm, Oakland, St. Clair and Washtenaw counties, the state health department announced. Those tests have yet to be confirmed by the Centers for Disease Control and Prevention.

Gov. Gretchen Whitmer urged Michigan residents to take precautions against the spread of the disease during a news conference with Chief Medical Executive Dr. Joneigh Khaldun on Thursday night.

Whitmer announced the closure of all school buildings and said she would make an announcement about the state work force "in the coming days."

She noted that the state's total of positive tests jumped from 2 to 12 within a day and expects "more to come."

"Even if you feel healthy and are asymptomatic, you can unknowingly be carrying and spreading the virus," Whitmer said. "Assume that you are and take these orders seriously.”

The new cases of coronavirus:

• An Ingham County woman who had been on a cruise.

• Three Kent County residents — two women and one man — who had a history of international travel.

• A Montcalm County woman who had traveled internationally.

• Two Oakland County men, one with a history of domestic travel and another who had not traveled recently. The county released a list of sites where people may have been in close contact with the men.

• A Washtenaw County woman and man, one who traveled domestically and another who traveled internationally.

• A St. Clair County man who had a history of domestic travel and is in stable condition at his home, where he is isolated. The man "took proper precautions" and had "minimal contact" with others.

The state is working local health departments to determine when the individuals' symptoms started, who they were in contact with "and assessing those individuals for symptoms as well," Khaldun said.

"The situation is rapidly evolving and we will continue to monitor the number of cases across the state," Khaldun said.

Whitmer said she understood her actions "will prompt a lot of questions."

"We’re going to do our best to answer as many as we can tonight but there are some questions that we need to spend more time to work to get through. I ask you to bear with us.”

The governor declared a state of emergency Tuesday night after announcing the first two cases, which involved a Wayne County man who traveled domestically and an Oakland County woman who had presumptively tested positive for COVID-19.

The city of Livonia said Thursday that the Wayne County man was a resident of the city and was isolated at University Hospital in Ann Arbor.

Samples that test positive at the state's lab are called "presumptive positive" until results are confirmed by testing at the CDC's laboratory in Atlanta.

Once transit and processing time are taken into account, the turnaround for each test batch is about 24 hours, Khaldun said.

Currently, the state lab has the capacity to process about 1,300 tests, and other private labs are coming online, Khaldun said.

"I'm telling clinicians, 'Do not hold back if you think it is appropriate for someone to be tested,' " Khaldun said. Nonetheless, she said, "... it is a possibility that we will run out of tests, so it is incredibly important that the federal government keeps up with that demand."

The state so far has approved testing for 135 people. One hundred and twenty have tested negative and 26 still are pending, meaning the state lab is waiting to receive the samples from the counties.

About 554 people have been referred for assessment or monitoring, and 172 remain under active monitoring.

On Thursday, Detroit Mayor Mike Duggan held a news conference to confirm that two Utah Jazz players who tested positive for COVID-19 stayed at a downtown Detroit hotel. Officials later confirmed it was the Westin Book Cadillac hotel.

eleblanc@detroitnews.com