Raids were underway in Brussels today as the manhunt continued for two suspects in this week's deadly bombings.
Seven people have been arrested in Brussels since late Thursday in connection with the ongoing investigation into the attacks that killed at least 31 people and injured at least 300, the Belgian federal prosecutor said. Police will decide today whether to charge those detained in the raids.
The arrests in Brussels came shortly after raids in northwest Paris that reportedly foiled another planned attack, French Interior Minister Bernard Cazeneuve said. He said the plot was in the “advanced stage” of preparation and that a French national was arrested in the raid.
The French plot had not been linked to the attacks in Brussels or those in Paris last November, but "is the result of weeks of investigation, of technical and physical surveillance, and close cooperation between European services," Cazeneuve said, adding the person arrested was involved in a “terror network” that planned to strike.
Investigators were still seeking a suspect in the Brussels metro bombing and another suspect in the airport bombing. The suspect in the metro bombing had been seen on surveillance camera footage inside the station with suicide bomber Khalid El-Bakraoui, a Belgian police source said. He can be seen carrying a bag and walking away, the source added.
The suspect in the airport bombing was also seen with Najim Laachraoui and Khalid’s brother, Ibrahim El-Bakraoui, who have been identified by police as the suicide bombers in the airport attack.
Police have not identified the suspect in the airport bombing, who can be seen in a surveillance image wearing a light-colored jacket, but a U.S. official said his name was already in U.S. terrorism databases at the time of the attacks.
Khalid and Ibrahim El-Bakraoui were also already in U.S. terrorism databases at the time of the attacks, U.S. officials said.
Belgium's federal prosecutor also confirmed there was an international and European arrest warrant for Khalid El-Bakraoui dating from Dec. 11, 2015. The warrant was linked to the Paris attacks. El-Bakraoui is suspected of renting a house in Charleroi, Belgium, which was used by the Paris attackers and raided on Dec. 9, 2015.
His brother, Ibrahim El-Bakraoui, was deported from Turkey in July 2015. According to a letter released by the Dutch Justice Ministry, the Turks did not provide any information on why Ibrahim was being deported, nor instructions on what to do with him. He was deported to the Netherlands, rather than Belgium, upon his request, according to the ministry's letter.
Belgian authorities were notified of Ibrahim's arrest near the Syrian border in June, 2015, but knew "nothing more than that," Belgian Justice Minister Koen Geens said.
In recent weeks and months, there has been consistent chatter about other terror plots planned for Europe, with specific locations and targets being discussed, a senior intelligence official told ABC News. New attacks could come at any moment, the official added.
Belgium lowered its threat level Thursday from the highest level, 4, to a 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.
Random checks at metro stations will continue as the subway system gradually reopens with an increased police and military presence in place.
The Brussels airport will not have passenger flights until Sunday.
ABC News' Pierre Thomas contributed to this report.