The two suspects are still being questioned, although no charges have yet been laid Two suspects have been arrested in relation to Monday's MTR arson attack, which left 14 people injured. One is a 55-year-old man with a history of mental illness. The man, surnamed Yee, was arrested at around 11pm on Monday after he sought treatment for burns at Tuen Mun Hospital, police said. Police last night arrested a second suspect, aged 65, at his home in On Ting Estate, Castle Peak, at about 11.45pm. The uninjured man was being detained for questioning at the estate. Neither suspect has been charged. It is understood that the younger suspect is an outpatient at Castle Peak Hospital - which specialises in treating the mentally ill - and is required to be on medication and see a doctor regularly. His last consultation was last week. The man lives alone and is not married. He has been on welfare since 2000. The man aroused suspicion among medical staff when he went to Tuen Mun Hospital's accident and emergency department to seek treatment for burns on his arm on Monday night. After receiving treatment, the suspect was arrested. He was hooded, handcuffed and escorted by detectives to Tuen Mun police station at about 4am yesterday. He was wearing a public hospital gown, pyjama pants and a pair of slippers. Following a brief interrogation at the station, he was taken to his third-floor apartment in Mei Tai House, Fu Tei Estate, in Tuen Mun where officers conducted a search and seized some evidence. Shortly before 6am, the suspect was driven to the headquarters of the Hong Kong Island regional crime unit in High Street in Western, where officers continued their investigation. Last night, commuter Gavin Kwai Sze-kit, hailed as a hero during the attack, went to the station to identify the suspect. Sources said the two arrested men were not suspected of being accomplices. Monday's attack took place in the first compartment of a Tsuen Wan line train as it was travelling from Tsim Sha Tsui to Admiralty, shortly after 9am. The arsonist reportedly started the fire with a bottle of thinner and a lighter. Four other bottles of thinner and five 250 gram cylinders of liquified petroleum gas were later found in the blackened compartment. Panic-stricken passengers ran for their lives from the carriage. The passengers were evacuated when the train arrived at Admiralty station, two minutes after the fire broke out. The arsonist fled in the confusion. The 14 injured passengers, suffering smoke inhalation and shock, were all treated then released from hospital on Monday. Senior assistant police commissioner Peter Yam Tat-wing said police presence at MTR stations had been stepped up and he was not worried about any copycat attacks.