LONDON — British police investigating the Manchester Arena attack cordoned off an area around a car significant to the investigation as they hunted Friday for clues about the suicide bomber’s movements.

Officers put a 100-meter (100-yard) cordon in place around a white Nissan Micra in southern Manchester. They want to piece together Salman Abedi’s preparations for the attack at the Ariana Grande concert that killed 22 people — and to learn whether others helped him.

“This is potentially a significant development in the investigation,” Detective Chief Superintendent Russ Jackson said. “We are very interested in anything people can tell us about the movements of this car, and who was in it, over the past months.”

Police were also interested in “who may have had access to the car or who may have gone to and from it.”

As a precaution, people were being evacuated from the nearby Ronald McDonald House, which offers accommodation for families with children who are being treated in the hospital. A local hospital remained working as usual and even managed to host a visit by Prince William, who met with children wounded in the attack.

The second-in-line to the throne later visited Manchester Cathedral, where he praised the grit of the city and those who responded to the attack.

“Manchester’s strength and togetherness is an example to the world,” he wrote in a book of condolence. “My thoughts are with all those affected.”

William also met with police officers, expressing his gratitude for the actions of those first on the scene of the blast. Among them was 47-year-old police constable Michael Buckley, who treated the wounded even as he frantically searched for his own child.

Buckley was off duty and waiting for his 15-year-old daughter Stephanie when the bomb exploded. He found himself in an arena’s foyer, which he described as a scene of “absolute devastation.”

“I knew my daughter was in there somewhere,” he said.

Even so, he tried to help others and kept trying to contact her in the confusion. She had suffered a concussion and some crush injuries.

“I eventually met her in a hotel in the early hours of the morning,” Buckley said. “She just ran to me and grabbed hold of me but I couldn’t hold her because I was covered in other people’s blood.”

In a city traumatized by the events of last week, police have released new security camera images of the Manchester bomber’s last moments, hoping to jog the memories of the public to see if someone might remember something.

Even those who knew Abedi struggled to explain his actions. His cousins, Isaac and Abz Forjani, expressed shock in a BBC interview.

“It’s not easy being connected to 22 lost, innocent lives,” Isaac Forjani said. “The fact that the person that did this is related to us by blood is something that’s going to stay with me for the rest of my life.”

The two brothers were arrested by police after the attack and released without charge.

Ten men, aged between 18 and 44, remain in custody on suspicion of terrorism offences in connection with the attack. Six others, including a 15-year-old boy, have been released without being charged.

Danica Kirka, The Associated Press