Ukraine appealed to Russia for a temporary ceasefire on Wednesday to allow repairs to be made to a power line to the Chernobyl nuclear power plant, warning that there could be a radiation leak if the electricity outage continued.

Ukraine’s state-run nuclear company Energoatom said fighting between Ukrainian and Russian forces made it impossible to immediately repair the high-voltage power line to the plant, which has been captured by Russian forces.

Energoatom said radioactive substances could be released if the plant cannot cool spent nuclear fuel, and Foreign Minister Dmytro Kuleba said reserve diesel generators can power the plant for only 48 hours. The UN nuclear watchdog said the loss of power does not have a critical impact on safety.

On Tuesday, the IAEA had warned that the systems monitoring nuclear material at the radioactive waste facilities at Chernobyl had stopped transmitting data.