(AP) — The Fort Calhoun nuclear power plant in eastern Nebraska has temporarily shut down due to ice buildup.

Omaha Public Power District spokesman Jeff Hanson said the plant went offline Thursday morning after subfreezing temperatures caused ice buildup on one of six gates used to control water from the Missouri River. The buildup kept the gate from fully closing.

The plant was closed because all the gates must be functional in case of flooding. The Nuclear Regulatory Commission was notified about the situation early Thursday after workers noticed the buildup hours earlier.

Hanson says workers have since cleared the ice and they are manually working on the affected gate. Once the affected gate is closed, the other gates can do the work and the plant can be back in service.