Gas cylinders stolen from Bedford ambulances
Gas and air cylinders have been stolen from ambulances outside an accident and emergency department.
Police are investigating four incidents of the canisters, which provide pain relief, being taken from Bedford Hospital.
The thefts occurred on consecutive days from 17 December.
The East of England Ambulance Service warned thieves that if used incorrectly the gas could be addictive and cause "serious brain damage".
Police are keen to talk to a man who was seen wearing a grey hooded top in the nearby Millbrook Road prior to the theft in the early afternoon of 18 December.