FILE - In this Oct. 3, 2017, file photo, investigators work among thousands of personal items at a festival grounds across the street from the Mandalay Bay Resort and Casino in Las Vegas. Friends and relatives of the victims and other concert-goers who survived returned Monday, Oct. 9, 2017, to reclaim baby strollers, shoes, phones, backpacks and purses left behind in the panic as they fled, at a Family Assistance Center at the Las Vegas Convention Center. (AP Photo/Marcio Jose Sanchez, File)

LAS VEGAS - They came quietly, in a steady stream looking for purses, wallets and cellphones. One person searched for a treasured wedding bracelet.

After the deadliest mass shooting in modern U.S. history, concertgoers and family members of those who attended a country music festival that ended in death for dozens of people sought Monday to recover belongings left behind in panic.

Lawn chairs, baby strollers, cowboy hats, boots and thousands of other items were discarded as 22,000 people fled the concert venue while bullets flew from the Mandalay Bay hotel casino across Las Vegas Boulevard.

FBI investigators spent a week combing the crime scene, carefully cataloguing evidence and separating personal items before transporting them to an assistance centre set up at the convention centre.

"I can just tell you from taking a look at it, it's just thousands and thousands of items, many, many truckloads that have been picked up," Clark County Emergency Manager John Steinbeck said. "More than I would have ever expected."

People are being allowed to retrieve the belongings in groups based on where they were seated at the concert. The items available for retrieval are those that were found in an area west of the stage, which included Americans with Disabilities Act-compliant seating, as well as those recovered from inside and in front of the VIP tent and bleacher seating east of the stage.

The sombre mood at the hall was occasionally deepened by weeping.

Volunteers filled out intake forms with detailed descriptions of lost items, and later, FBI victims' assistance agents asked follow-up questions.

People received their belongings in re-sealable plastic bags. After identifying their items, some smiled and others hugged the FBI agents or Red Cross volunteers who helped them.

Those returning to claim their items first must pass must through a vehicle checkpoint. Prominent signs indicate that no members of the media are allowed. Police SUVs are parked a few feet away from the entrance.

Officials restricted access to the assistance centre to protect the privacy of victims and those traumatized by the shooting.

News from © The Associated Press, 2017