The cooling system for a fuel storage pool at one of the reactors at the Fukushima nuclear plant has failed, Japanese regulators have said.

There was no immediate danger from the failure, the second at the plant in a month, they said.

The Fukushima plant was severely damaged by the March 2011 tsunami that devastated Japan's north-east coast and suffered multiple meltdowns. It is currently in the process of being decommissioned.

A spokesman for the Nuclear Regulation Authority said an alarm went off on Friday afternoon at reactor No 3, and that the cause of the failure was still under investigation.

A spokesman for the plant's operator said it would take two weeks before temperatures approach dangerous levels following a cooling system failure.

Last month, a power cut caused a two-day failure in a cooling system.