16 have been arrested so far in connection with the Manchester Arena attack, but it is thought the 22-year-old operated on his own

Police now believe the Manchester bomber acted largely alone in the run-up to his suicide attack at Ariana Grande’s concert.

Soon after Salman Abedi blew himself up at Manchester Arena eight days ago police said they were investigating a potential terror “network”. But now detectives say the 22-year-old shopped alone for most of the components he used to make the bomb, which killed himself and 22 concertgoers on 22 May and injured 116 more.

“Our inquiries show Abedi himself made most of the purchases of the core components and what is becoming apparent is that many of his movements and actions have been carried out alone during the four days from him landing in the country and committing this awful attack,” said Det Ch Supt Russ Jackson, head of the north-west counter-terrorism unit.

Abedi was born in Manchester to Libyan parents, who moved back to Tripoli in recent years, along with his younger siblings. He is believed to have visited Libya just four days before the attack, arriving back in the UK on 18 May.

His father and younger brother, Hashem, have been taken into custody by Libyan authorities.

Police are not ruling out that Abedi may have had accomplices. “It is vital that we make sure that he is not part of a wider network and we cannot rule this out yet. There remain a number of things that concern us about his behaviour prior to the attack and those of his associates which we need to get to the bottom of,” said Jackson.

Police have arrested 16 people so far in connection with the investigation. Three men were released without charge on Tuesday: two men aged 20 and 24 from the Fallowfield area of south Manchester, believed to be Abedi’s cousins, and a 37-year-old man from Blackley in north Manchester. A 16-year-old boy from Withington and a 34-year-old woman from Blackley were released last week shortly after their arrests.

Police have examined Abedi’s phone records, along with CCTV footage, to begin to piece together his movements in the run-up to the attack. The investigation has 3,000 lines of inquiry within the counter-terrorism control room, with officers examining almost 300 pieces of digital equipment, including phones.

“Much of the investigation has been painstakingly working through Salman Abedi’s last movements. We have done this by examining his movements on CCTV and other interactions he has had whether it be with people or the phone calls he has made,” said Jackson.

“With specialist support we have also have a good understanding of the likely component parts of the bomb and where these came from.”

On Monday night police released a CCTV image showing Abedi wheeling a large blue suitcase and appealed for anyone who may have seen him with it on Wilmslow Road, known locally as the Curry Mile because of its abundance of south-Asian restaurants.

“We are especially keen to find out why he kept going back to the Wilmslow Road area and we need to find the blue suitcase which he used during these trips,” said Jackson. For the last few days officers have been searching a landfill site in Pilsworth, Bury, reportedly looking for the case.

Eleven men remain in custody, mostly in their late teens or early twenties. Suspects can be held without charge for up to 14 days if arrested under the Terrorism Act.

“We still have a number of people in custody and we will be seeking to extend the custody of some of them as we work to understand what has gone on and whether Abedi was helped,” said Jackson.

“The release of some people can be expected in investigations of this nature as we corroborate accounts that have been provided.”

Anyone with information should call the anti-terrorist hotline in confidence on 0800 789321.