Transport expert Hung Wing-tat said on Tuesday that a train derailment at Hung Hom Station could have been caused by cracks in the city's ageing railway tracks.
An East Rail Line train split in two during the morning rush hour in what was Hong Kong's first derailment of a train carrying passengers in decades.
Hung, from the Hong Kong Society for Transportation Studies, said objects on the tracks could also have caused the accident and the MTR Corporation must now carry out an inspection of the whole line.
"The railway company has to have a thorough check on each section of the railway line to ensure there is not fatigue or minor cracks in the rail," he said.
"There's another possibility that there was an outside object that fell onto the rail and that may be more serious. It means that there should be some sort of failure ... people should not be able to throw things on the rail."
At least three people were taken to hospital after the accident at around 8.30am, and hundreds of passengers had to clamber across the tracks to safety.