Two victims were in intensive care and six of the injured were rescue workers exposed to fumes from chemicals that spilled from the train that derailed near the city of Ghent, officials said yesterday.
A 64-year-old man died of asphyxiation after inhaling toxic fumes, provincial governor Jan Briers said.
The accident and blaze happened around 2:00 am (0000 GMT) on Saturday and prompted authorities to evacuate around 300 people from their homes.
Fishing and water sports in the area were banned.
More From This Section
The victims were people living well away from the scene of the accident, and Interior Minister Joelle Milquet blamed toxic fumes from the highly flammable liquid chemicals for their injuries.
Six of the train's 13 wagons derailed and two were left lying on their sides, said Infrabel, the state-owned company that operates Belgian railways.
The blaze led to a series of explosions in the railway wagons, then a spectacular strip of fire spread over hundreds of metres prompting authorities to evacuate residents living within 500 metres of the scene of the accident.
Exposure to acrylonitrile can cause headaches, dizziness, nausea and mucus membrane irritation.
Milquet said toxic fumes reached much farther, via the drainage system, than the 500-metre perimeter that was set up.
"Some of the chemical product went into the drains and caused a kind of chemical reaction with gases that are toxic and escaped into certain streets beyond the perimeter that had already been evacuated due to the fire," she said.
Firefighters let the wagons burn out in a controlled manner as water could have released further toxic chemicals.