Regulators in Britain said Saturday there is no evidence that a fire on a Boeing 787 “Dreamliner” parked at London’s Heathrow Airport was linked to the lithium battery failures that grounded the model of airplane for months. 

The Air Accidents Investigation Branch (AAIB) probe of the fire is just getting under way and is expected to take several days, the agency said. Preliminary findings indicate the plane, operated by Ethiopian Airlines, sustained “extensive heat damage” in the upper portion of the rear end of the fuselage, which is a “complex part of the aircraft.”

“However, it is clear that this heat damage is remote from the area in which the aircraft main and APU (Auxiliary Power Unit) batteries are located, and, at this stage, there is no evidence of a direct causal relationship,” the agency said Saturday.

The fire was seen by a witness who told investigators there was smoke throughout the fuselage.

Ethiopian Airlines, in a news release issued Friday, said the plane was empty and had been parked at the airport for more than eight hours.

The Dreamliner was touted as a revolutionary aircraft when Boeing rolled out the model last year, in part because of its lithium-ion battery system to reduce energy consumption during flights.

But a series of battery failures this year, including one that sparked an electrical fire, prompted the Federal Aviation Administration (FAA) to ground the Dreamliner in January. The FAA approved a fix in April, allowing the plane to resume flights.

The FAA, the National Transportation Safety Bureau, Boeing and Ethiopia Airlines have each been invited to participate in the investigation, according to the AAIB.

“The sole objective of the investigation is to determine the causal and contributory factors of this serious incident, with the intention of preventing a recurrence,” the agency said. “It is not the purpose to apportion blame or liability.”