"We confirm this information," the union said, asked whether the police officers massively called in sick.
Earlier in the day, local media reported that the police officers took a sick leave to express their protest against extra hours caused by staff shortages.
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The Belgian Interior Ministry did not rule out the possibility of collusion between the police officers and medical workers who signed the sick leave notes. Issuing false medical notes is punished in Belgium by fines and prison sentences up to several years.