Seeking to avert a meltdown, Japanese officials injected seawater into overheating nuclear reactors on Sunday, relieving pressure at a nuclear plant in Fukushima prefecture, according to a report.

The No. 3 reactor at the Fukushima No. 1 plant may have been deformed due to overheating, Chief Cabinet Secretary Yuko Edano said, according to Kyodo News.

He denied that there had been a meltdown at the plant. Such a condition occurs when nuclear fuel rods melt in the reactor.

He also said another hydrogen explosion could take place at another reactor in the facility, similar to one on Saturday that blew off part of the building which housed another reactor at the same plan.

The reason is that large amounts of hydrogen formed when a water injection procedure ran into some temporarily problesm that may have filled part of the building housing reactor No. 3, Edano said.

Plant operator Tokyo Electric Power Co. began injecting water into the No. 3 reactor's core vessel on Sunday, according to the report. 

An evacuation area of 12 miles around the plant has been in place since Saturday, after bein expanded from 6 miles.