The UK Air Accidents Investigations Board (AAIB) confirmed on Tuesday that it has “invited” Honeywell, the maker of the emergency locator transmitter in the Boeing 787, to join the investigation into the fire that erupted last Friday in an Ethiopian Airlines Dreamliner parked at London Heathrow Airport. It would not, however, specifically identify the ELT as the ignition source.

“The emergency locator transmitter [ELT] is one several components being looked at in detail as part of the investigation, and it would be premature to speculate on the causes of the incident at this stage,” said an AAIB spokewoman. “The traveling public can be sure we are investigating all possible causes and following up all leads.”

The incident happened less than two months after aviation authorities lifted orders grounding all Boeing 787s in service following two cases of overheated batteries. The grounding lasted some four months and cost Boeing millions of dollars in contract penalties and thousands of man-hours of research and testing of the eventual fix.

The most recent fire emanated from near the rear of the airplane, however, far from the areas that house the lithium-ion main ship battery, located in the forward electrical equipment bay near the nose of the jet, and the APU battery, which sits in the aft electrical equipment bay in the belly of the fuselage near the wings.

“There has been extensive heat damage in the upper portion of the rear fuselage, a complex part of the aircraft, and the initial investigation is likely to take several days,” said the AAIB in a statement. “However, it is clear that this heat damage is remote from the area in which the aircraft main and UPU batteries are located, and, at this stage, there is no evidence of a direct causal relationship.”

Boeing and Ethiopian Airlines each issued brief statements acknowledging the event, but neither offered much detail. “Smoke was detected from Ethiopian Airlines B787 aircraft with registration number ET-AOP, which was parked at London Heathrow airport for more than eight hours,” said Ethiopian. “The aircraft was empty when the incident was observed. The cause of the incident is under investigation by all concerned.”

Boeing's share price, which had dipped after news of the fire broke on Friday, quickly recovered after it emerged that the incident appears to have had no connection with the lithium-ion ship batteries.