Seven people have been arrested in connection with a spate of thefts of nitrous oxide cylinders at a Staffordshire hospital.
The arrests follow an attempted burglary at Cannock Chase Hospital at 01:30 GMT on Friday.
A woman, 47, and six men, aged between 20 and 39, all from the Norwich area, were arrested on suspicion of burglary.
More than a dozen gas cylinders have been stolen from two Staffordshire hospitals in the past week.
Three men forced their way into a storage room at the same hospital last Saturday and took 13 bottles of nitrous oxide.
Then on Wednesday, a storage room at County Hospital in Stafford was broken into and two oxygen cylinders were taken.
All seven arrested were travelling in three vehicles in Winson Green, Birmingham.
Ch Insp Sarah Wainwright, of Cannock Chase district local policing team, said: "These arrests are a result of shared intelligence and collaborative working between Staffordshire Police and our colleagues at West Midlands Police, Norfolk Constabulary and the Central Motorway Police Group.
"We will continue to work alongside them as our investigation continues."