Two people were injured when a staircase collapsed.
One had to be airlifted to hospital in Stoke on Trent and the other driven to Ysbyty Gwynedd after the incident on Saturday.
The accident happened on Caernarfon Road in Bangor at what is believed to be an industrial premises.
Exact details of the incident have not been revealed, but it is believed a portable staircase used in a workshop may have collapsed or fallen over.
A spokesman for the Welsh Ambulance Service said both casualties were conscious, but gave no further details of injuries.
North Wales Live has approached the Health And Safety Executive for information but has so far had no response.
