The Latest: 3 ordered held in Belgium on terror charges

Right wing demonstrators run on flowers as they protest at a memorial site at the Place de la Bourse in Brussels, Sunday, March 27, 2016. In a sign of the tensions in the Belgian capital and the way security services are stretched across the country, Belgium's interior minister appealed to residents not to march Sunday in Brussels in solidarity with the victims. (AP Photo/Geert Vanden Wijngaert) (The Associated Press)

Right wing demonstrators protest at a memorial site at the Place de la Bourse in Brussels, Sunday, March 27, 2016. In a sign of the tensions in the Belgian capital and the way security services are stretched across the country, Belgium's interior minister appealed to residents not to march Sunday in Brussels in solidarity with the victims. (AP Photo/Valentin Bianchi) (The Associated Press)

Riot police attend a memorial site during a protest by right wing demonstrators at the Place de la Bourse in Brussels, Sunday, March 27, 2016. In a sign of the tensions in the Belgian capital and the way security services are stretched across the country, Belgium's interior minister appealed to residents not to march Sunday in Brussels in solidarity with the victims. (AP Photo/Valentin Bianchi) (The Associated Press)

The Latest on the attacks on Brussels in which 31 people died (all times local):

11:25 a.m.

Belgian prosecutors say three people have been ordered held on charges of participating in terrorist group activities

They were among four people detained during Sunday searches in Brussels and the northern cities of Mechelen and Duffel.

Belgian prosecutors did not release details on the alleged terrorist actions or whether they were linked to the March 22 suicide bombings at Brussels airport and in the Brussels subway.

The fourth person has been released without charge, according to a statement from the Belgian Federal Prosecutor's Office Monday.

Those charged by the investigating magistrate were identified only as Yassine A., Mohamed B. and Aboubaker O.

10:45 a.m.

A week after devastating suicide bomb attacks, Brussels Airport will test its capacity to partially resume passenger service. But it's too early to say when service might actually resume, an airport official said Monday.

Florence Muls, the airport's external communications manager, said 800 staff members on Tuesday will test temporary infrastructure and new arrangements designed for passenger check-in. The Belgian government must approve the new system, Muls said, before Brussels Airport can resume handling passenger traffic.

Two suicide bombers on March 22 caused great damage to the airport's departure hall, and along with another suicide bomber who blew himself up on a Brussels subway train, killed at least 31 people and injured some 270.