British police say they have arrested a sixth person as they continue investigating a “network” over the attack at a pop concert in Manchester that killed 22 people, some of them children, and injured 64.

According to Reuters, British police arrested a sixth person, a woman, in connection with Monday's suicide bombing in Manchester, on May 24 following searches in Blackley, an area north of the city center.

“These searches are connected to Monday's horrific attack on the Manchester Arena, but this is a fast moving investigation and we are keeping an open mind at this stage,” police said in a statement.  “A woman has been arrested at an address in connection with the investigation.”

Earlier, the BBC reported that armed police had made the arrest during a raid on a block of flats.

British Interior Minister Amber Rudd said the May 22 attack was “more sophisticated than some of the attacks we've seen before, and it seems likely -- possible -- that [the bomber] wasn't doing this on his own.”

Rudd told the BBC it appeared that the bomber, identified by the police as British-born Salman Abedi, 22, had recently returned from Libya.   Abedi was of Libyan descent.

Rudd said she was “not surprised at all” that the Islamic State terror group claimed responsibility for the attack, but that there was no information yet to confirm the extremist organization's active direction.

The suspected bomber's father, Ramadan, and younger brother, Hashem, have reportedly been arrested in the Libyan capital, Tripoli.

Hashem was arrested on suspicion of links with the IS group, according to Reuters news agency.

British police arrested the older brother, Ismael, on May 23.

They said the fifth suspect they arrested earlier on May 24 was carrying a package, which they were still assessing.

The British-Libyan community in Manchester released a statement condemning the bombing as “an attack on all of us.”

Meanwhile, police investigating the Manchester Arena bomb attack have stopped sharing information with the US after leaks to the media, the BBC said.

UK officials were reportedly outraged when photos appearing to show debris from the attack appeared in the New York Times.

It came after the name of bomber Salman Abedi was leaked to US media just hours after the attack.

Theresa May is to raise concerns with Donald Trump at a NATO meeting later, according to the BBC