Update, March 11, 8:55 p.m.: Denver’s Cory Elementary School will remain closed for a second day on Thursday, March 12, after a parent of two students tested positive for the new coronavirus.

“We are still awaiting further information from health officials on the results of the testing of our students of the Cory parent who has tested positive for COVID-19,” says a letter from Principal Joan Wieser.

Colorado Gov. Jared Polis issued rules Wednesday for school closures in the event a staff member or student tests positive for coronavirus. But in cases where a student’s immediate family member tests positive, Polis left the decision up to school district leaders. The rules do say the student should be tested.

“Schools may choose to close for 24 hours based on the immediate family member, caregiver, or guardian’s positive test while waiting for the student’s test results,” the guidance says.

If a student or staff member tests positive, a school must close for at least 72 hours “for cleaning and social distancing,” the rules say. If a school has three or more cases, it must close for at least 14 days.

Original story, March 11, 8:20 a.m.: A Denver elementary school is closed Wednesday because a parent of two students there “has a confirmed case” of the new coronavirus, the district said in a letter sent to families Tuesday night.

Cory Elementary School in southeast Denver is closed “out of an abundance of caution,” the letter says. Cory serves about 400 students in grades one through five. This is the first public school in Colorado to close in response to the new coronavirus.

“We will take this time to thoroughly disinfect the school, including common areas and classrooms,” says the letter, which is signed by Principal Joan Wieser. “We will be in daily contact with our Cory families to share up-to-date information. The health and wellness of our students and staff are the district’s highest priority.”

The letter does not say when the school will reopen.

The Colorado Department of Public Health and Environment is working to determine who the parent had contact with, the letter says. The parent’s two children who attend Cory are also being tested for the new coronavirus, or COVID-19, it says.

As of Tuesday evening, 17 Coloradans had tested positive for COVID-19, according to the Colorado Department of Public Health and Environment. They include five people in Denver, including a woman in her 30s, a woman in her 40s, a man in his 40s, a girl in her teens, and a woman in her 70s. Tests in a sixth case have been “indeterminate.”

Public health authorities expect the number of positive cases to rise as testing becomes more available. On Tuesday, Gov. Jared Polis declared a state of emergency as Colorado tries to slow the spread of the virus.

Two students who attend Denver’s East High School, the city’s largest school, have been under quarantine after they had contact with a family friend who has been diagnosed with COVID-19.

At least two Denver private schools have closed for cleaning in connection with COVID-19. They include St. Anne’s Episcopal School, where a parent tested positive for the virus, and Mullen High School, which does not have any confirmed cases.

The virus is spread by people breathing in droplets emitted from infected sneezes or coughs, and also between people who are in close contact, according to the Centers for Disease Control. It is also thought to spread by someone touching contaminated surfaces and then touching their mouth or nose. It appears that children face less risk in contracting the illness.