Japan's top safety official said on Wednesday that the damaged battery in the All Nippon Airways 787 Dreamliner that made an emergency landing last week did not appear to be overcharged, although it did not rule out the possibility.

Norihiro Goto, Japan Transport Safety Board chairman, was speaking to reporters at a media briefing.

On Sunday, U.S. safety investigators ruled out excess voltage as the cause of a battery fire earlier this month on a Boeing Co 787 passenger get operated by Japan Airlines and said they were expanding the probe to look at battery's charger and the jet's auxiliary power unit.

(Reporting by James Topham; Editing by Chris Gallagher)