POLICE are continuing to search a landfill site for a suitcase believed to contain materials discarded by the Manchester Arena bomber and have released new pictures of him in the days leading up to the attack.

The last people arrested in connection with the bombing have now been released from custody.

Detective Chief Superintendent Russ Jackson, head of North West County Terrorism Policing, said that officers now have a 'deep understanding' of Salman Abedi's movements into and out of the country in the weeks leading up to the attack and how the chemicals and equipment were obtained and where the bomb was assembled.

He added that they now have an understanding of where Abedi had been in the days before the explosion, which killed 22 people and seriously injured many more, almost hour by hour.

Mr Jackson said: "We said at the start we had to rapidly understand whether this was an attack committed by an isolated individual or a wider network and we have made enormous progress in this and are far more confident on who was not involved and who could still be involved.

“The terrorist investigation has involved officers drawn from across the national Counter Terrorism Policing Network, from the National Crime Agency and police forces across the country. More than 1000 officers have been involved.

“Within the first hours after the attack, a dedicated counter terrorism operation room had been established to co-ordinate the policing response and the hundreds of staff involved in the hunt for any further potential attackers, and anyone who had helped Abedi to carry out his attack.

“A dedicated specialist team was set up to co-ordinate the identification of those who had been killed and also to support their families. Each of the families received the support of specially trained family liaison officers and this will continue. More than 200 people were injured in the attack and a dedicated team was put in place to work with them and keep them informed of progress in the investigation.

“In the first few hours after the attack the priority of the investigation was to identify the attacker. This urgent work was needed to identify any other threats or possible further attacks. Within two hours Abedi’s identity was known through the work of forensic teams who attended the scene.

“In such investigations we try to piece together the last movements of the attacker and understand if they were helped. This has been one of the main lines of inquiry in this case."

In total 22 people were arrested in relation to the attack and they have all now been released without charge.

Twenty-nine houses have been searched for evidence of explosives and connections to the attacker and evidence of explosive material at several locations. Each of the location has links to Abedi.

Hundreds of witnesses have been interviewed and hundreds of hours of CCTV have been examined.

Around 700 devices including phones have been seized and are being examined for evidence.

Mr Jackson said: “Each of the 20 detained people have been interviewed many times and they have been questioned about their associations and contacts with Abedi. During the investigation, we have uncovered a number of suspicious purchases of materials by individuals which can be used to make explosives.

"We have identified contact with Abedi that occurred close to the attack time and in some cases the presence of people of interest to the inquiry in Manchester City Centre on the evening of the attack. Although this is not the case for every person, it is factors such as these that have led us to make arrests.

“Some of those arrested and now released have offered accounts which explain innocent contact with Abedi and we are, at this time, satisfied with these explanations. However, this has taken a considerable amount of time to work through to ensure we are satisfied and that the risk to the public has been considered. As more information comes in it will be acted upon immediately.

“It appears that in the final days Abedi sought to transfer money out of the country and this has taken some time to understand in the context of the contacts he made in the hours running up to the attack."

He added that it is clear Abedi left the UK on April 15 and travelled to Libya, returning on May 18 and purchasing more items for the bomb.

Abedi has been tracked buying nuts from a DIY store that were used for shrapnel as well as the tin that police believe the explosive was placed in.

He was also tracked going to and from the Banff Road area of Rusholme.

Mr Jackson said: "It is in Rusholme where the White Micra was found and in it considerable evidence. The Micra contained materials for bomb making and Abedi is forensically linked to the car. We know the vehicle was purchased on the 13 April and it was only in his possession for a short period time because he flew out on the 15 April. Because of this we believe items were stored in it during that time, either materials to make a bomb or a pre-made charge. The actual assembly of all the parts appears to have been in the days immediately before the attack.

“We are still working on the detail of this and continue to appeal to the public for help if they have seen this R registration Micra being used and if they have seen anyone going to and from the Micra at Devall Court after 13 April.

“We are especially interested in movements on 14 April as we believe this was a crucial date in the car being parked with bomb components in it."

Officers have been searching a landfill site in Pilsworth, Bury for a blue suitcase and this is expected to continue for some time.

Police believe this contains items Abedi discarded after having assembled the bomb and it could contain crucial evidence.

Mr Jackson said: "Our enquiries show that the assembly of the device is likely to have been by Abedi himself. What is less clear is whether he acted alone in obtaining the materials for the device before he left the country on 15 April and whether others knew or were complicit in the storage of materials knowing what was being planned. Understanding this is crucial to our work in the coming weeks and months."

New images of Abedi and the car have been released as well as pictures of barrels stored in the car as police continue to appeal for information.

Mr Jackson said: “This is very much a live criminal investigation moving at considerable speed. It is a terrorism investigation relating to 22 murders and multiple attempted murders. It will continue at its current pace as we work to understand the full extent of the involvement of anyone else. We will be speaking with more people. Work around CCTV, financial transactions and telephone contacts will continue as we piece together the movements of Abedi in fine grain detail.

“Hashem Abedi, the brother of Salman Abedi, left the country at the same time as the attacker on 15 April. Hashem Abedi is currently detained in Libya, there is much media reporting about what he has said in Libya and we wish to interview him in relation to this attack.

“This was a premeditated, calculated and vicious attack. It was planned carefully and has caused devastation and heartbreak to so many. We have a massive team still working flat out on it and there are critical lines of enquiry at home and abroad which we will relentlessly pursue.”