Two students at Cardiff University say their belongings were thrown away while they were in lockdown.
The university said their property would not be touched, the pair claimed.
Meg Bridges said cleaners had entered her room and her belongings were "bagged up." Upha Barclay said she had about £400 worth of items thrown out.
She said potentially hundreds of people were affected. The university said it was apologising to and compensating students "where appropriate."
Ms Bridges said she heard about what was happening from a friend who had remained in halls.
"On my desk there was a bag of clothes," the journalism student from Tenby said.
"Some pictures that had been hanging on the wall had been broken."
Soil was on the floor where a plant had been thrown away, the 19-year-old added.
Liquid had also been spilled on her pictures.
"I cried to my mum because I was so shocked," Ms Bridges said.
Medical student Upha Barclay, 20, said she had lost about £400 worth of non-perishable food and kitchenware bought for her as gift.
Ms Barclay, travelled from Devon for "essential belongings" after receiving a message online.
"I found a bag in the corridor that appeared to be waiting ready to be taken away," she said, adding that she believed "hundreds" of students might have been affected.
Cardiff University said it had been clearing rooms for healthcare students going to work for the NHS.
It said some items that "were unhygienic" had been disposed of from shared areas.
Items from communal areas that could be safely stored would be, it said.
"We recognise we have made an error in cleaning out one student bedroom," a spokesman said.
"We are dealing with any students affected by this on an individual basis, apologising and recompensing where appropriate."