Police tracking down leads connected to the Paris terror attack last November engaged in a shootout in Brussels, Belgium Tuesday that lasted for several hours. One suspect was killed by a police sniper but two more escaped and are still on the run.

The shootout began when a group of Belgian and French police arrived at what they believed was an empty apartment in a suburb of Brussels. CNN reports:

The raid began around 2:15 p.m. (9:15 a.m. ET) Tuesday when four Belgian and two French police officers arrived at what was thought to be an empty residence in Forest, according to a senior Belgian counterterrorism official.

Instead, Van der Sypt said, “From the moment that the door of the flat was opened, at least two persons … opened fire toward them.”

Three officers — including a Frenchwoman — were hurt in the initial exchange of gunfire before managing “to retreat safely,” he said.

Reinforcements arrived, with bullets flying back and forth for several hours. Another officer, from Belgium, suffered a slight injury to the head in the later exchange.

Belkhaid Mohammed, a 35-year-old Algerian man was shot and killed by a police sniper when he attempted to fire a weapon at police from a 2nd story window. However two other suspects managed to escape through another window. This CNN clip shows the scene where the shootout, and the escape, took place:

Once inside the apartment, police found a Kalashnikov rifle, ammunition, an ISIS flag and a book on Salafism. The Telegraph has details on the suspects who escaped:

According to Dernière Heure, the two suspects at large are thought to be Khalid and Ibrahim El Bakraoui, respectively 26 and 30. Known for gangster-related crimes, the name of one has cropped up in anti-terror investigations, according to Le Monde.

After the standoff, police and special forces expanded their search and homed in on a neighbouring street, rue de l’Eau, after finding two gun cartridges and dark clothing in the area. During a raid on a house, they picked up another Kalashnikov.

Two suspects were arrested overnight – one after checking into hospital with a broken leg, another during a raid on a house near the gun fight. Both were later released without charge on Wednesday.

The two men who were arrested later are apparently not the same two who were in the apartment. In all, Belgian police have arrested 23 men in connection to the Paris raids so far and an additional 58 suspected militants who are not believed connected to the raids. Police are still searching for Salah Abdeslam, a Belgian militant with connections to ISIS who was directly involved in the Paris attack.

A day after the raid in Belgium there was a separate raid in Paris. Four men who are believed to have been plotting an attack in France were arrested.