LANZHOU - Students and teachers in Northwest China's Gansu province who are currently trapped in their school due to a flood are safe and have enough food for two to three days, local education authorities said Thursday afternoon.

Over 100 middle school students and teachers at the Maiji Junior Middle School in the city of Tianshui remain trapped after the school, which is located in a mountainous area, was isolated by a rainstorm-triggered flood that washed away the only bridge linking the school to the outside, the provincial education department said.

The floodwaters have started to retreat and will not threaten the safety of the trapped people, but the school's gate and some of its walls were destroyed in the storm, which has been battering the city since Wednesday night.

The school is a boarding school with dormitories and cafeterias, said Chen Baolin, deputy director of the education bureau of the city's Maiji District.

The school's cafeteria can supply the trapped students and teachers with enough food for two to three days, Chen added.

Another 28 schools in the city were affected by the rain.

The Lanzhou Central Meteorological Station issued a red alert for continuous rain in Gansu on Thursday, adding that there is a high risk of rainstorm-triggered floods and geological disasters.

China has a four-tier color-coded weather warning system, with red alerts issued for the most serious weather conditions, followed by orange, yellow and blue.