LONDON – Police investigating the Manchester bombing freed three more people without charge, including the bomber’s brother, and released more photos Tuesday as they worked to reconstruct the killer’s final movements.

The May 22 attack at an Ariana Grande concert killed 22 people as well as bomber Salman Abedi, a Briton of Libyan descent. Police are trying to uncover clues about a suspected network that supported him.

Greater Manchester Police released photos of a white Nissan Micra seized in Manchester, saying “significant evidence” had been found inside.

Police appealed for anyone who saw the car between April 13, when its previous owner sold it, and April 15 — when Abedi left the U.K. — to contact detectives.

Police say Abedi returned to Britain from Libya four days before the attack. Detective Chief Superintendent Russ Jackson said “Abedi made repeated trips to and from this car” during those four days, “and we believe he was taking items from the car to help assemble the device.”

Police also released a photo of a sports bag with a San Francisco 49ers logo, saying anyone who recognized it should contact them.

Police arrested a total of 18 people over the attack, but have released 10 of them without charge. Eight remain in custody.

Among those released was Ismail Abedi, the dead bomber’s brother, arrested a day after the attack. A 20-year-old man arrested May 27 and a 33-year-old man arrested May 24 were freed without charge on Tuesday. Their names were not released.

The bomber’s father, Ramadan Abedi, was arrested in Tripoli on May 24, along with another brother Hashim, who Libyan security forces said was “aware of all the details” of the attack.

The Islamic State group has claimed responsibility for the attack.