Northeast China was slammed by unusually cold temperatures and blizzards on Monday, which resulted in the rescheduling of hundreds of flights, the closing of schools, and the issuance of increased weather alerts and warnings to stay indoors in numerous cities.

As of 7 p.m. (1100GMT), 90% of Jilin province’s expressway gates were closed due to up to 25 centimeters of snow, according to official media CCTV.

The local railway operator in Heilongjiang, the northernmost province of the country, stopped 51 passenger routes due to safety concerns.

A gymnasium in Heilongjiang’s Jiamusi city collapsed, trapping three inside, according to CCTV.

State-run Jimu News said there were children at the venue at the time of the incident. It is unclear if the collapse was related to the snowfall, the report said. A rescue operation is underway.

Schools, kindergartens, and off-campus training institutions in most parts of Harbin, capital of Heilongjiang, will remain suspended on Tuesday, after they were cancelled on Monday, CCTV said.

China’s national weather forecaster renewed its orange blizzard alert – the second highest tier of its color-coded warning system – at 6 p.m, as more snow is expected from Monday night to Tuesday in parts of Jilin and Heilongjiang.

Earlier on Monday, 405 flights were cancelled at Harbin Taiping International Airport, according to data from third-party travel app Flight Master.