Members of Manchester suicide bomber Salman Abedi’s network are still potentially at large, British interior minister Amber Rudd said on Sunday, after the terrorism threat level was lowered because of significant progress in the investigation.

Police said they have arrested a large part of the network behind the bombing, which killed 22 people at a concert hall, and three more men were arrested over the weekend as police continued to close in on the group.

Asked during an interview on BBC television whether some of the group were still at large, Rudd said: “Potentially. It is an ongoing operation. There are 11 people in custody, the operation is still really at full tilt in a way.”

Greater Manchester Police said on Sunday that they had arrested a 14th person in connection with the attack. The 25-year-old man was detained in the southwest of the city on suspicion of terrorism offenses. Police were also searching another address in the south of Manchester.

Prime Minister Theresa May said developments in the investigation into the bombing meant that intelligence experts had decided to lower the threat level from its highest rating “critical,” meaning an attack could be imminent, to “severe.”

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