Authorities in Japan have turned their gaze toward GS Yuasa, the maker of the batteries which have caused concern on the troubled Boeing 787 Dreamliner.

Working alongside counterparts from the United States, investigators are working to establish what caused an All Nippon Airways 787 to make an emergency landing due to an apparent battery malfunction.

However, another US regulator said on Sunday the battery did not overcharge in a separate incident involving a Japan Airlines (JAL)-operated 787.

All Dreamliners currently in operation have been grounded while the investigation continues, while Boeing has also stopped deliveries of the plane while the fault is investigated.

Yasuo Ishii, a Japanese transport ministry safety official, said earlier: “Engineers from the Federal Aviation Administration in the United States, Boeing and our aviation bureau started a probe this morning that is mainly focusing on the production line at GS Yuasa.

“They are checking on whether there have been any issues in the production process.

Japanese battery maker GS Yuasa has seen its shares fall 11 per cent since January 7th when an electrical fire broke out on a JAL 787 at Logan International Airport in Boston.