An abandoned suitcase was noticed by a conductor on the service from the Belgian coastal resort of Ostend to the airport on the outskirts of the capital at about 4.45pm on Wednesday.
When the conductor opened the case he found bags of suspicious white powder and raised the alarm. Emergency services feared the powder could be anthrax.
The train was stopped at Denderleeuw station in Flanders, which was soon swarming with police and the fire brigade.
Passengers were forced to remain on the train for the next three hours, until 8pm, before being hosed down.
Firefighters donned special protective seats to retrieve the bag, as seated travellers, who were given food and water, looked on.
“We were treated well by the emergency services, but there are nicer places to spend the evening,” one of the travellers told local media.
Belgian authorities said it would not be clear whether the powder was deadly anthrax or not until later today at the earliest. Mayor Jo Fonck visited the scene.
He told the Het Laatste Nieuws newspaper, The packaging was not damaged, which fortunately makes the risk of contamination of the travelers extremely small.
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