A Seattle elementary school will remain closed Friday after a norovirus outbreak.

John Muir Elementary School closed Thursday as crews followed a cleaning and disinfecting process outlined by the King County Department of Health.

Principal Brenda Ball Cuthbertson said she decided to close the school for cleaning on Thursday after "a significant number of students exhibited symptoms of norovirus."

The school initially reported it would reopen Friday. The district said in a tweet that the building is clean and ready for students, but many staff and students are still sick.

Stomach flu type symptoms can appear within 12 to 48 hours after exposure to the virus. People can be contagious for 48 hours after symptoms have stopped.

Cuthbertson said students who have been ill should be kept home even after they feel better to help stop the virus from spreading.