6 Arrested in Brussels Police Operation After French Raids Foil Planned Terror Attack

Six people have been arrested in a large police operation in Brussels, a Belgian prosecutor said Thursday night, as two suspects in the deadly Brussels bombings remain on the loose.

The six arrested were detained for questioning, a Belgian prosecutor said in a statement. The decision of whether to charge them is expected to be made tomorrow.

Belgian Interior Minister Jan Jambon tweeted earlier in the evening that five people had been arrested.

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Several houses were searched in Brussels, Schaerbeek and Jette, the prosecutor said. The police raids were conducted in connection with the Brussels terror attack investigation.

News of the raid came shortly after raids in northwest Paris foiled a planned attack, French Interior Minister Bernard Cazeneuve said.

The French plot was at the "advanced stage" of preparation and was discovered after a French national -- described as being at a "high level" in the plot -- was arrested this morning, Cazeneuve said.

There did not appear to be links "at this stage" between the plot foiled in France and the Paris or Brussels attacks, he added, saying the arrest is the result of weeks of investigation and the individual was involved in a "terror network" that planned to strike.

The raids in Argenteuil, about 8 miles outside of the center of Paris, were ongoing and the streets were sealed off.

Investigators are actively seeking a second suspect in the Brussels metro bombing who has been seen on surveillance camera footage inside the subway station with suicide bomber Khalid El-Bakraoui, a Belgian police source told ABC News.

That second suspect, who is unidentified, was spotted on the subway platform at the Maelbeek station with El-Bakraoui, according to police.

El-Bakraoui is thought to be dead after detonating a bomb on the subway train as it was pulling out of the station. The accomplice now being sought has yet to be identified, but police do not believe he died in the Tuesday attack.

In the other attack at the city's international airport, Khalid El-Bakraoui’s brother, Ibrahim El-Bakraoui, was one of two alleged suicide bombers who led that attack.

Najim Laachraoui and a man wearing a light-colored jacket, who has not yet been publicly identified by police, were with Ibrahim El-Bakraoui at the airport, as seen on a surveillance camera image released by authorities.

Laachraoui is believed to be dead after detonating his suicide bomb, while the unnamed man has been the subject of a manhunt since Tuesday's attacks, as Belgium lowered its threat level today from the highest level, 4, to 3. Paul Van Tieghem, director of the office that evaluates threats to the nation, said there is no indication that another attack is imminent but the threat is still serious and possible.

The first suspect that is being sought was pictured on the airport surveillance footage. His identity remains unknown, but he stood out in the photo because he was the only one of the three suspects pictured not wearing a black jacket. As a result, he's been widely referred to as the "man in white."

There has been some speculation that the "man in white" was a handler or supporter for Laachraoui and El-Bakraoui since he was not wearing a glove on his left hand like they were, which may have been hiding a trigger, and his bomb failed to detonate until after it was secured by law enforcement.