A 60-year-old man has been arrested and accused of arson, Hong Kong police said at press conference Friday.
Online video of the incident at Tsimshatsui MTR station showed bystanders beating out flames on the lower body of a man whose pants had been burned away, while a fire burned in a nearby carriage.
Both chief executive contenders Carrie Lam and John Tsang said they felt shocked at the incident, and expressed their condolences to the injured, reported RTHK.
"Extra travelling time can be expected on the Tsuen Wan Line. More details to follow", the MTR said in a statement on its official website.
Hong Kong's counter-terror units were deployed to the scene, but there were conflicting reports on how the blaze started.
Smoke and flames filled the packed rush hour carriage at Tsim Sha Tsui station in Hong Kong.
"MTR staff are handling the situation", it said.
A Twitter account for the metro system said: 'The Tsuen Wan line accident was due to a passenger igniting unsafe goods. "There was nothing we could do but to inhale the smoke".
"A free MTR shuttle bus service is operating between Tsim Sha Tsui Station and Yau Ma Tei Station, through Jordan Station; or please consider using other transport", the MTR said.
"One minute we were all playing with our phones, the next there was smoke everywhere".
A video posted on social media shows a man lying on the platform with his pants are on fire, whilst the public attempt to put it out. "There were many people and it was impossible to run", she said. Kwok told reporters the man, whose pants appeared to be completely burned, was likely to be Cheung. However, police later said the attack isn't being treated as a terrorist incident.