Belgian prosecutors opened an investigation on Wednesday after an email was sent threatening a bomb attack on the Brussels metro.
Police carried out searches on the network but found no device and none of the 69 stations were closed, while authorities said an attack appeared unlikely.
“All threats are taken seriously,” the national crisis centre said. “This is also the case of the mail that warned of an attack today in the Brussels metro.”
In March 2016, the Brussels metro and the city’s international airport were targeted in suicide bomb attacks that killed 32 people and were claimed by the Islamic State group.
