Japan’s Transport Safety Board says the lithium ion battery aboard a Boeing 787 flight in Japan last month found evidence of the same type of “thermal runaway” seen in a similar incident in Boston.

The board said in a report Tuesday that CAT scans and other analysis found damage to all eight cells in the battery that overheated on an All Nippon Airways 787 on Jan. 16, prompting an emergency landing.

They also found signs of “thermal runaway,” a chemical reaction in which rising temperature causes progressively hotter temperatures. U.S. investigators found similar evidence in the battery that caught fire last month on a Japan Airlines 787 parked in Boston.

All 50 Boeing 787s in operation are grounded as regulators and Boeing investigate the problem.