“There is a lot of information coming out at the moment — about what happened, how this occurred, what people might or might not have known,” Ms. Rudd said in an interview with Sky News. “And I think it is right that the MI5 takes a look to find out what the facts are.”

She emphasized, however, that while the investigations into possible security failures would be useful, the main focus should be on the terrorism investigation that is also underway.

Detectives investigating the attack said Friday that they had arrested most of the members of the network believed to have assisted Mr. Abedi on his suicide mission.

The police carried out a series of armed raids across Greater Manchester over the weekend that ended with the arrest of a 25-year-old man in the Old Trafford area of the city. The operation expanded on Monday to Shoreham-by-Sea, on the southeastern coast of England, where counterterrorism police officers arrested a 23-year-old.

That brought the number of arrests in the case to 16, the Greater Manchester Police said in a statement on Monday. Of those, two people have been released without charge.

The police released a new image of the bomber on Monday that showed him wheeling a blue suitcase through Manchester city center days before he carried out the attack.