The helicopter that crashed in Broome on Saturday — killing two people — went into a spin just after receiving clearance to take off, the head of the nation’s transport safety watchdog says. Air safety experts have began investigating the fatal accident, which killed Kimberley business identity and pilot Troy Thomas, 40, and a 12-year-old girl who is yet to be identified. Mr Thomas’ daughter Mia, 12, and Mandurah teacher Maddison Down, 24, were also aboard the helicopter. Tonight, they are still in hospital in a serious but stable condition. The incident happened about 2.25pm after the Robinson R44 chopper launched from the Horizontal Falls Seaplane Adventures headquarters in Bilingurr, north of Broome. The helicopter was owned by the renowned tourism company, founded by Mr Thomas 14 years ago. Two Australian Transport Safety Bureau helicopter experts arrived in Broome to begin the investigation yesterday, with another two expected to fly up to the Kimberley town today. ATSB chief commissioner Greg Hood said today that air traffic control had provided clearance for the helicopter to become airborne about 5km north of Broome International Airport, before observing it climb “above the tree tops” and enter a spin. He said evidence gathered during the investigation would include company, pilot and maintenance records, as well as electronic data, weather conditions, CCTV footage and witness statements. “If there are any safety issues identified during the course of our investigation we will of course bring those immediately to the attention of the aircraft operators and the regulator,” he said.The Federal agency is expected to release a preliminary report within 30 days. Kimberley District Supt Greg Crofts said the helicopter would be moved from Antheous Way in Bilingurr, where it crashed, to a vacant shed at Broome International Airport for examining by the ATSB experts. “Police have been maintaining the site since Saturday to secure it and prevent any interference, while also launching a separate investigation into the two deaths themselves,” he said. Supt Crofts said the incident had been traumatic for all those involved. “Many people are doing it tough because of this, it has had a huge impact on the Kimberley in an awful way,” he said. “People who responded or witnessed the crash have seen things they will never be able to forget and we can only hope that the two survivors fully recover from their injuries.” West Kimberley Insp. Gene Pears told media on Sunday that all passengers on the chopper were known to each other. He said police were at a very preliminary stage of the investigation into the deaths. Insp. Pears said the accident could have been far worse given it happened in a built-up area. The ATSB is an independent Canberra-based Commonwealth agency established to improve safety in aviation, marine and rail transport by investigating major accidents and other safety lapses.