Dangerous drugs were stolen from an ambulance while crews were dealing with a patient.
People have been warned not to take the drugs, which were stolen along with medical equipment and a satellite navigation system.
The theft happened while the ambulance crews were in a house in Bourneside Road, Addlestone, Surrey on Monday.
Officers said anyone who found the drugs should take precautions and hand them to police.
Appealing for witnesses, a police spokesman asked anyone who may have seen youths near the ambulance, or in the road, to contact the force.
Drugs taken in the theft between 1815 BST and 1830 BST included GTN spray which, if incorrectly used, can cause black outs and cerebral bleeds. It is also explosive
Liquid Salbutamol was also stolen, which is for breathing problems, and can cause heart problems if the person taking it is drunk.
Glucagon and Hyperstop were taken, which are prescribed for diabetes - two needles were stolen that were already made up.
And Atrovent in a plastic cylinder was taken, which is used for breathing problems, and which can be life-threatening if used with oxygen.
A quantity of aspirin tablets also went missing.
Equipment stolen included two blood pressure kits, a micro-vent which is an automatic pump for an oxygen bag, and oxygen masks.