Three or four people drove into a Brighton hospital car park and stole six cylinders of gas and air in an early hours raid.
They used a car with stolen number plates to plunder the laughing gas from a store at the Royal Sussex County Hospital in Brighton.
Sussex Police said: “Police have released CCTV images of people wanted in connection with the theft of six Entonox gas cylinders from Royal Sussex County Hospital in Brighton.
“Three or four offenders used stolen number plates on a red Ford Fiesta to drive into the hospital car park before they entered a store room and took the items.
“The incident occurred at about 2.43am on Tuesday 18 July.
“Officers are keen to identify the suspects and gather information as the bottles may be dangerous if used incorrectly.
“Anyone with any information is asked to report it online quoting serial 103 of 18/07.
“Alternatively, you can visit the Crimestoppers website or contact the independent charity anonymously on 0800 555111.”
The force said that Entonox – half oxygen and half nitrous oxide – is used for pain relief. It is colloquially known as gas and air, laughing gas or nitrous.