Paris has seen the biggest and certainly its swiftest manhunt now in recent years. In less than 48 hours, police have arrested 23 people and seized arms including rocket launchers in 168 raids overnight. Another 104 people were put under house arrest, Interior minister Bernard Cazeneuve told journalists.

One of the killers had been stopped and fingerprinted in Greece last month, fuelling speculation the Islamic State had taken advantage of the recent influx of refugees fleeing the Middle East to slip militants into Europe, Prosecutors said.

Ismael Omar Mostefai:

The first to be identified was named as Ismael Omar Mostefai, a 29-year-old who lived in the city of Chartres, southwest of Paris. French media said he was French-born and of Algerian descent. Molins said the man had a security file for Islamist radicalization, adding that he had a criminal record but had never spent time in jail.

A judicial source said Mostefai’s father and brother had been taken in for questioning, along with other people believed to be close to him. Another source said police had found a car in a suburb east of Paris that was believed to have been used in the assault, suggesting that at least one of the attackers had escaped.

Abdelhamid Abaaoud:

A French official has identified the suspected mastermind as Belgian Abdelhamid Abaaoud, AP reported on Monday. Abaaoud is reported to be in Syria.

A source close to the investigation said Belgian national Abdelhamid Abaaoud, currently in Syria, was suspected of having ordered the Paris operation. “He appears to be the brains behind several planned attacks in Europe,” the source told Reuters.

Abdeslam Salah:

The French authorities on Sunday said that the Paris terrorist attacks were carried out with the help of three French brothers living in Belgium, and asked for the public’s help in finding one of them. The authorities also said that they were seeking Abdeslam Salah, 26, whom they described to be dangerous. The police warned the public: “Do not intervene on your own, under any circumstances.”

Abdeslam Salah’s  brother Ibrahim had died in the three-hour massacre on Friday night, which killed at least 132 people, Belgian officials said, adding that another brother, Mohamed, was detained on Saturday in the Molenbeek area of Brussels.

French officials initially described eight attackers, but on Saturday night, they announced that only seven had died — six by blowing themselves up and one in a shootout with police. They said on Sunday that they were looking for an eighth man believed to have been involved in the attacks. It was not immediately clear on Sunday evening whether Abdeslam Salah was that eighth man.

Police raided homes of suspected Islamist militants across France overnight following the Paris attacks. The investigation into the coordinated Paris attacks led swiftly to Belgium after police discovered that two of the cars used by the militants had been rented in the Brussels region.

Belgian officials said they had arrested seven people in Brussels while another man — one of three brothers believed to have been involved in the plot — was being hunted. French prosecutors said they have identified five of the seven suicide attackers who died on Friday. Four were French while the fifth man was fingerprinted in Greece in October and was possibly Syrian.