( CNN ) -- A fire that broke out Friday in an empty Boeing 787 Dreamliner at London 's Heathrow Airport does not appear to be related to the jet 's batteries , the UK Air Accidents Investigation Branch said Saturday . `` It is clear that this heat damage is remote from the area in which the aircraft main and APU batteries are located and at this stage there is no evidence of a direct causal relationship , '' the agency said in a statement . No injuries were reported , but the cause of the fire inside the Ethiopian Airlines plane was not clear . The incident puts Boeing 's marquee 787 Dreamliner fleet back in the headlines after it was grounded this year because of a fire risk associated with the planes ' batteries . The U.S. National Transportation Board said Saturday that it sent an investigator to London to aid in the investigation . Senior Air Safety Investigator Lorenda Ward was to be accompanied by NTSB airplane systems investigators and representatives of the Federal Aviation Administration and Boeing . Japanese Dreamliner held due to A/C power glitch . Ethiopian Airlines said in a posting on its Facebook page that the incident occurred on one of its jets after it arrived Friday morning on a normal flight from Addis Ababa to Heathrow . After passengers deplaned and the plane was cleaned , it was towed to a remote area , where it was parked and its internal and external power switched off , Ethiopian said . `` After more than 8 hours smoke was detected , '' it added . The Air Accidents Investigation Branch said no one was aboard the plane when the fire broke out , causing `` extensive heat damage '' to the upper portion of the rear fuselage . It predicted the initial investigation would take several days . Another 787 Dreamliner flying out of the United Kingdom and operated by Thomson Airways was forced to turn back Friday after what the airline called `` a technical issue . '' The 787 Dreamliner represents a new generation of efficient wide-body , long-range aircraft , and Boeing has placed a big bet on the fleet . Customer demand for the Dreamliner has remained solid despite the grounding . The plane is more efficient than earlier models due to its lighter weight , using composite material rather than aluminum and wires instead of some of the hydraulics . Another Dreamliner diverted for mechanical problem . Although Boeing has delivered to customers just 68 of the planes , it has 862 unfilled orders . Boeing says it plans to increase production to 10 per month by the end of the year , double the rate earlier this year . The first of the long-delayed Dreamliners went into service for Japan 's All Nippon Airways in October 2011 , and the planes flew without major problems for more than a year . But after the battery problem emerged in January , the company had to retrofit the 50 Dreamliners already in service before they could return to service . Though Boeing shares sank Friday 3.6 % on the news , they were still up more than 30 % since the start of 2013 .
Fire broke out Friday at London 's Luton Airport . No injuries were reported in the incident . Boeing 's marquee aircraft was grounded this year because of a fire alarm .