Authorities captured a suspect linked to the Brussels bloodshed Wednesday following a massive manhunt, as details emerged of the suicide attackers: two brothers who brought chaos and bloodshed to the city at the heart of European unity, according to two senior European officials.

The identity of the arrested suspect was not immediately released. Belgian media reported that the suspect was 24-year-old Najim Laachraoui, whom European security officials had previously described as a suspected Islamic State bombmaker.

One senior Belgian official said that an arrest had been made in connection to the probes into Tuesday’s attacks that left at least 31 people dead in bombings at the Brussels Airport and a metro station. The Islamic State claimed responsibility.

But that official, as well as another European intelligence official familiar with the case, said that Laachroaui was not the person arrested.