Thousands of tributes left by the public in memory of those killed or injured in the Manchester Arena terrorist attack are to be preserved and digitised.

The Manchester Together archive, held at Manchester Art Gallery, is made up of more than 10,000 items left at memorial sites that sprang up across the city in the weeks following the 22 May 2017 attack, which killed 22 concertgoers.

The gallery has received a £99,700 grant from the National Lottery to photograph the items and create a searchable online archive. The money will pay for two members of staff to set up the archive and recruit and train 15 volunteers to photograph every item that was collected.

The items include letters, drawings, poems, soft toys and balloons, many of which were left in St Ann’s square, where around 300,000 floral tributes were laid. Among the objects found alongside the flowers were Great Manchester Run medals and a grip-seal bag of Glastonbury mud.

The archive has been visited by a number of those who lost loved ones in the attack and the project’s organisers said they were exploring its possible use in therapy to help families with the grieving process.

Sir Richard Leese, the leader of Manchester city council, said the archive was part of a promise the city had made never to forget the victims of the attack. “In St Ann’s Square, we saw the public stand shoulder to shoulder with those who had been most closely affected, an act of impressive solidarity that signified our refusal to give in to hatred,” he said.

“I am glad that those expressions of solidarity will be preserved and kept. They are now part of Manchester’s rich history and we should remember and reflect upon them.”

Amanda Wallace, the deputy director of Manchester Art Gallery, said: “From scribbled notes on scraps of paper to beautiful paintings and poems, everything that was left in St Ann’s Square is an important part in the story of what happened here.

“I am committed to providing a permanent home of the archive at Manchester Art Gallery and excited about the opportunities for developing, interpreting and digitising this material for the public benefit.”

The project has also included an initiative to dry out and clean nearly 2,000 teddy bears and give them to new homes after photographing them. An army of Women’s Institute members from branches across Greater Manchester set to work repairing the toys before sending them to local charities to distribute.