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MANCHESTER (AP) – Manchester’s police chief has told reporters that it is clear “this is a network we are investigating” as he gave an update on the probe into the bomb attack at an Ariana Grande concert, killing 22 and injuring dozens others.

Chief Constable Ian Hopkins said Wednesday that police are carrying out extensive searches across Manchester as part of their probe.

British police said officers arrested a fifth suspect, and are assessing a package the suspect was carrying.

Greater Manchester Police said the suspect was detained in Wigan, a town to the west of Manchester. The force did not immediately provide details.

Officers also arrested three men earlier Wednesday in Manchester.

Another man, the brother of alleged bomber Salman Abedi, was arrested on Tuesday.

Witnesses say they heard explosions as police raided a block of flats in central Manchester.

Residents described how armed police and men clad in balaclavas stormed the Granby House building, an apartment block where rented apartments are popular with students and young professionals.

Muye Li, a 23-year-old student who lives on the third floor, says he heard an explosion as police stormed an apartment on his floor.

He says officers knocked on his door and “asked me if I had seen the lady next door,” and believed police were looking for a woman.

Hopkins declined to comment on whether police have found the alleged maker of the explosive device used in Monday night’s attack.

His comments followed media reports that the alleged bomber, Salman Abedi, acted as a “mule” for others.

Hopkins says a serving police officer was among the 22 people confirmed killed in the attack.

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