Five people were released from police custody in Belgium on Monday after having been briefly detained in connection with last month's Paris terrorist attacks, amid reports that police are searching for a person who had contact with the attackers.
Investigators in neighbouring France and Belgium have been trying to piece together how the November 13 attacks at a concert hall, national stadium and a string of bars and restaurants in central Paris were organized. They left 130 people dead.
The Belgian newspaper Het Nieuwsblad wrote Monday that the attackers - seven of whom died on November 13 - were in touch shortly before the killings with two mobile phones in Belgium.
The contacts included an ominous text message reading "We're off we're starting" that was sent from a mobile phone later recovered from a litter bin near the Bataclan concert hall in Paris, the French newspaper Le Parisien reported on Sunday.
Investigators believe that a person in possession of the Belgian mobile phones may have coordinated the Paris attacks, according to Het Nieuwsblad.
Belgian police carried out a search in the centre of Brussels on Sunday evening in connection with the hunt for that person, but the suspect remains at large, local media reported.
Prosecutors said in a statement that three people were taken into custody for questioning during the search, two of them brothers. Two more people were then detained during a second search on Monday morning in the Brussels suburb of Laken.
But all five people were ordered released on Monday afternoon by a magistrate, the prosecutors said.
"The investigation continues unabated," they added.
Belgian police have detained dozens of people following the Paris attacks, with most later released. But eight people have been arrested on terrorism charges, half of them for allegedly having helped Paris suspect Salah Abdeslam flee after the attacks.