A Belgian judge has opened an investigation for possible manslaughter over floods that claimed 38 lives, the prosecutors office in Liège has announced.

The investigating magistrate has the task of identifying who might be responsible for "involuntary homicide by lack of foresight or precaution" the prosecutors office said in a statement.

Liège, in the French-speaking region of Wallonia in the south of the country, was worst hit by the disaster.

Questions are already being asked in the aftermath of the flooding over 14 and 15 July, specifically over possible failings in the flood alert system.

Some of those caught up in the disaster have said that they had had no warning that a dam at Eupen, in the east of the country, which was overwhelmed by the waters, had its sluice gates opened - before all the locals had been evacuated.

The latest provisional death toll stands at 38, federal police told AFP, contradicting a figure of 41 given by the head of Wallonia's regional government, Elio Di Rupo.

Neighbouring Germany was also hit hard by the flooding, which claimed the lives of more than 180 people there.