A loud noise was heard outside a reactor building at Fukushima nuclear plant as the operator of the plant cleared away debris, Tokyo Electric Power Co (Tepco) told Reuters on Tuesday.

However, no one was injured and there was no change in radiation levels at the plant's monitoring posts, a Tokyo Electric official told reporters.

People at the plant suspect that the loud noise might have come from a gas cylinder in the debris, the official said.

Tepco said that more details on the cause of sound will be released on a planned daily briefing at 4 a.m. EDT after gathering all the information.