Police investigators at the Makkasan station were alerted via the 199 emergency hotline at 3.42pm about a fire involving an air-conditioned passenger bus (Route No 206, Kasetsart University to Mega Bangna) near the Airport Rail Link station on Asok-Din Daeng Road in Huai Khwang district. Firefighters and rescue personnel were dispatched to the scene.
Initial reports indicated that a freight train had collided with a bus and a motorcycle, triggering a fire, reports the Bangkok Post.
Flames engulfed the bus within minutes. Explosions were heard intermittently as firefighters battled the flames and eventually brought them under control. Rescue workers later discovered the bodies of eight passengers inside the bus.
Bangkok Governor Chadchart Sittipunt said the train travelling from Laem Chabang Port to Bang Sue in Bangkok struck the bus that had become stuck on the railway tracks amid heavy traffic.
Eyewitnesses told reporters that before the incident, they noticed the rail crossing barrier appeared to be malfunctioning. Video posted online of the moment of impact appears to show the barrier stuck in place.
Mr Chadchart said traffic congestion reportedly prevented the barriers from operating properly, causing the train to crash into the bus and drag it for about 50 metres before the bus caught fire.
Authorities are reviewing recordings of radio communication between the barrier operator and the train driver, following reports that the latter did not respond when told that vehicles were stuck on the tracks.
As the bus was dragged along after impact, it struck a number of other cars and motorcycles, which also caught fire.
Thirty-five other people in cars and motorcycles were injured, according to a police update. Officials were providing first aid and transporting them to nearby hospitals for urgent treatment. Two of those injured were reported to be in critical condition.
Rescue teams transported the eight bodies to the Police General Hospital shortly after 7pm for identification and to notify relatives.
The Ministry of Transport, the State Railway of Thailand and the Bangkok Mass Transit Authority (BMTA), which operated the bus, are monitoring the situation.
Mr Chadchart, Deputy Transport Minister Siripong Angkasakulkiat and BMTA director Kittikan Chomduang Jaruworapolkul are at the scene to oversee the response and monitor developments.