File photo of a All Nippon Airways' Boeing Co's 787 Dreamliner plane at Haneda Airport in Tokyo

A US regulator has released details on the investigation into the battery fire-related issues on Boeing's Dreamliner aircrafts, although it failed to provide a conclusive answer to the cause of the fire.

The report from the National Transportation Safety Board (NTSB), released along with other related documents, said that investigations to find the cause behind the fire are continuing.

The regulator said that it is planning to schedule an investigative hearing on the 787's battery design and certification. It is also planning to hold a forum on lithium-ion battery safety issues in the same month.

Dreamliner is one of Boeing's most sophisticated jets, touted to have used revolutionary technology that could help to achieve improved fuel efficiency. But the craft had come under safety concerns after a Japan Airlines (JAL) carrier caught fire at the Boston Airport.

According to NTSB report, the aircraft cleaning personnel found smoke near the aircraft's kitchen immediately after it landed in Boston's Logan International Airport from Tokyo's Narita. A technician who was inspecting the area near the electronics bay "found heavy smoke and fire coming from the front of the auxiliary power unit battery case".

The airport's security videos had shown smoke emanating from the jet. The report said that two clear flames of about three inches were visible in front of the battery case.

NTSB is running extensive inspections on the burned remains of the battery and the certification and testing systems of Boeing. However, the regulator's decision to hold hearings have surprised many, as the battery problems had not led to any bigger catastrophe.

"It's unusual to have hearings when you haven't had a major incident," said John Hansman, co-chairman of an FAA advisory committee and a professor of aeronautics at the Massachusetts Institute of Technology told Reuters.

Hansman said that such public scrutiny could drag the process of the investigation itself and trigger a conservative approach.

"They don't want to look like they're being rash," he added.

Dreamliners across the globe continue to remain grounded and it is unlikely that the jets would be allowed to take off without the US regulators providing a green signal.

Japan