Six people were arrested in a series of police raids carried out around Brussels late on Thursday, the Guardian reports, in connection with Tuesday’s bombings. Also on Thursday, two Belgian officials offered to resign, as evidence mounted that the country failed to adequately prepare for the attacks

Two suspects in the deadly bombing were thought to be still at large Thursday as police carried out raids around Brussels. From the Guardian:

The operation involving Swat teams and armoured cars with helicopter support began soon after 9pm. RTBF, the state broadcaster, cited police sources as saying it had targeted “people suspected of taking part in the attacks” that killed at least 31 people and injured 300.

Federal prosecutors confirmed six unidentified people were arrested, including three who were detained outside the prosecutors’ own office in the centre of Brussels.

Two others were arrested in the Belgian capital, and one person was arrested in Jette, on the city’s outskirts.

Both the Belgian interior minister, Jan Jambon, and the justice minister, Koen Geens, offered their resignations on Thursday. Jambon admitted that there had been “errors at Justice and with the Belgian liaison officer in Turkey,” and that “if you put everything in a row, you can ask yourself major questions” about how the government dealt with the threat of European ISIS militants returning to Belgium from Syria.

The prime minister, Charles Michel, refused their resignations, Jambon said, telling him, “In time of war, you cannot leave the field.”

Earlier on Thursday, a French man in the “advanced stages” of a terror plot was arrested on the outskirts of Paris.