Japan's transport safety authority is looking into whether a false alarm caused a United Airlines plane to make an emergency landing last week.



The US carrier's Boeing 737 took off from Narita Airport near Tokyo and was heading for Cebu in the Philippines when the cockpit received a warning indicating a fire in the cargo hold.



The plane made an emergency landing at Kansai International Airport in Osaka. Five passengers sustained minor injuries during evacuation.



Two officials from the government's Transport Safety Board began on-site inspections on Saturday. They found no soot or other traces of fire in the cargo hold.



The board believes that the smoke sensor in the cargo hold or the fire alarm system may have malfunctioned. It plans to analyze flight recorder data.



The inspections will end on Monday. One of the officials, Takahashi Mitsuru, says the board will see whether accounts of people involved and other information obtained at the site will be consistent with the flight recorder data.