TOKYO: US and Japanese officials Saturday began analysing the black box of the 787 plane forced into an emergency landing this week, prompting the worldwide grounding of Boeing's Dreamliner, broadcaster NHK said.

The instrument will allow experts probing Wednesday's incident to reconstruct events leading up to the pilots aborting the flight due to a smoke alert apparently linked to the lithium-ion battery.

Investigators on Friday released a picture showing the blackened remains of the battery in the All Nippon Airways plane, which has remained on the tarmac in Takamatsu in southwest Japan.

The black box contains electrical data from the flight and will allow investigators, including a US team from the National Transportation Safety Board, to assess how the battery was affected.

According to the NHK report, the plane captain saw three alarms that prompted the emergency landing -- the first alerted the pilots to smoke in the compartment containing the battery, a second noted a voltage drop in the battery and the third was related to abnormal battery charging.

The risk of fire from overheating powerpacks has emerged as a major concern for Boeing's cutting-edge new planes since the incident on the domestic flight in Japan, which prompted airlines to ground all 50 of the world's operational 787s.

GS Yuasa, the Japanese company that made the battery installed in the ANA Dreamliner, said on Thursday the probe into the incident could take weeks.

A prolonged grounding could seriously compound problems for Boeing, which suffered a series of glitches over 10 days leading up to the ANA incident including another smoke alert on a Japan Airlines Dreamliner at Boston airport.