BRITISH investigators said yesterday a transmitter made by the US firm Honeywell was one of several components that may have caused a fire on a Boeing Dreamliner in London last week.

"We can confirm that Honeywell have been invited to join the investigation," a spokesman for Britain's Air Accident Investigations Branch said yesterday.

"The emergency locator transmitter (ELT) is one (of) 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."

The AAIB is leading the probe into a blaze on an Ethiopian Airlines jet that broke out last Friday and has already allayed fears about a return of problems with overheating batteries that grounded the Boeing 787 for months earlier this year.

A source said on Monday that investigators were now looking into whether the fire, which occurred at Heathrow airport, was caused by the battery of an ELT built by Honeywell.

Honeywell said at that point only that it had joined the investigation into the fire, declining to discuss details beyond saying it had no previous experience of difficulties with this type of transmitter.

The ELT, which is positioned in the upper rear part of the new airline, sends a signal that leads rescuers to downed aircraft. It is powered by a non-rechargeable lithium-manganese battery.

The focus on the emergency beacon raised alarms for some analysts, who said more technology problems with the new, high-tech airliner would be troubling.

"It's good to see the AAIB are getting closer to finding out what happened but what we really need to know now is if this is a one off or a problem for the whole Dreamliner fleet - that is the crucial point for Boeing and airlines," said Howard Wheeldon, an aerospace analyst.