The Air Accidents Investigation Branch said in a report that the greatest damage to the parked Ethiopian Airlines Dreamliner occurred around the aircraft's Rescu406AFN emergency locator transmitter near the tail section of the plane.
Investigators said it was not clear if the fire was caused by the transmitter's batteries or a short near or around the transmitter, but recommended that the Federal Aviation Administration switch off the Honeywell transmitter in all Boeing 787s "until appropriate airworthiness actions" can be carried out.
A spokeswoman for the investigation branch said the easiest way to make the transmitter systems "inert" — as set out in their recommendations — would be to take out their batteries.
Investigators also recommended that the FAA and other regulators carry out a safety review of lithium-battery powered transmitters in other types of aircrafts.
Spokespeople for Honeywell and the Federal Aviation Administration did not immediately respond to requests for comment.
When news of the Ethiopian Airlines' blaze at first broke last week, investors in Boeing were worried that the lithium ion battery problem that had grounded the whole 787 fleet in January for four months had not been fixed. However, the AAIB said early on there was no evidence that was the case in the Heathrow incident.
On Thursday, Boeing Co. said it supported the British investigators' recommendations — which it called "reasonable precautionary measures" — and was working with regulators to take appropriate action in response.
"We are confident the 787 is safe and we stand behind its overall integrity," the company added.
Shares in Boeing were up almost 2.5 percent at $107.34 in morning trading on Wall Street.
Associated Press writer Josh Freed in Minneapolis contributed to this report.
Copyright 2013 The Associated Press.