MANCHESTER, England -- Police are into their fourth day of raids and arrests as they try to dismantle what they are calling a "network" that they believe was behind the Manchester suicide bombing.

As CBS News' Mark Phillips reports, the authorities say they're making progress -- but not enough progress to lower the national threat level from "critical," which means they believe another attack could still be imminent.

On Friday morning, police raided a barbershop in the same Moss Side area of south Manchester where the bomber had lived. Police cut their way into the shop early in the morning and were seen removing materials, including what appeared to be a laptop computer.

Another merchant in the area said bomber Salman Abedi had been seen at the barbershop from time to time, talking with other people.

The shop has been suspiciously empty since the bombing, notes Phillips, and what once seemed like a normal neighbourhood, no longer does, according to some who live there.

Lewis Coatman told CBS News that he was "just amazed how one night everything is fine," and then "out of the blue," it all changed without warning.

After another arrest overnight, police were holding eight people on Friday. Ten have been detained but one man and one women were quickly released without charge.

Authorities are still not sure, however, that the terror network -- including its presumed bomb-making capability -- has been neutralized.

The spat between Britain and the U.S. over the leaking of evidence from the investigation, particularly the publishing of photos showing parts of the bomb by American news outlets, does appear to be over, meanwhile.

Manchester police are now sharing information with their U.S. counterparts again, after Prime Minister Teresa May and President Trump met in Brussels on Thursday.

The sense of anxiety, meanwhile, continues. In the latest move, armed police have been placed on some trains in the U.K. -- more as a confidence building measure than in response to a specific threat, it seems.