Airline safety regulators in Britain say the initial investigation into the cause of a fire in a 787 Boeing Dreamliner is expected to take several days. The U.K. Air Accidents Investigation Branch is taking the lead on the investigation of the fire in the Ethiopian Airlines jet that severely damaged the plane on Friday, while it was on the ground without passengers on board at a remote runway at Heathrow Airport in London. Investigators said there was no evidence the fire involved the battery system that was the cause of a global grounding of 787 Dreamliners for three and a half months starting with a series of fires on 787 jets in January. The Wall Street Journal reported Monday that Boeing has been asked to participate in the investigation. Boeing says it has to take a back seat to official investigators regarding public disclosures of progress of the case. \"Protocol dictates that all publicly released information concerning the investigation must come from, or be approved by, the AAIB,\" the company said. Several airlines said they would continue to fly their 787 Dreamliner jets while keeping an eye on the investigation. Ethiopian Airlines said it is still using its other three Dreamliners. U.S. airline company United Continental Holdings Inc., All Nippon Airways Co. of Japan and Japan Airlines Co. said they were keeping tabs on the investigation. British regulators said Friday\'s fire was \"serious.\" Sources briefed on the incident said the fire was concentrated overhead in the last few rows of the plane, the Journal said.