LONDON (AP) — British police say the man who bombed an Ariana Grande concert in Manchester wasn't part of a large network, but other people involved in the attack may still be at large.

Russ Jackson, head of counterterrorism policing for northwest England, said Thursday that police may make more arrests in the investigation.

Salman Abedi, a Briton of Libyan heritage, detonated a knapsack bomb as crowds were leaving Manchester Arena on May 22, killing 22 people and himself.

In the days after the attack, police arrested 22 people on suspicion of terrorism offenses and said they had rounded up a large part of Abedi's network. But all the suspects were subsequently released without charge.

Jackson says detectives want to question Abedi's younger brother, who has been detained in Libya.