Five people went missing when a speedboat overturned Friday on a reservoir on the Yellow River in northwest China's Gansu province, local authorities said.

The accident happened at 1:20 p.m., when five hydropower workers were maintaining a high-voltage wire on a reservoir at the Yanguoxia Hydropower Station in Yongjing county of Linxia Hui autonomous prefecture, provincial safety supervision authorities said in a press release.

The maintenance work was performed after another reservoir located upstream discharged floodwaters, creating problems for the station's wiring facilities.

Rescuers are searching for the five missing workers. An investigation into the cause of the accident is under way.