A large quantity of prescription medication, intended for animal use, was stolen from a veterinary clinic in Basingstoke.
According to police, one of the preparations could cause a severe reaction which could prove life-threatening if inhaled, consumed orally or injected.
It can be found in a bottle branded 'Iso-Flo' and contains Isoflurane.
Police are warning people to not take anything that is not prescribed to them and not intended for human use.
Anyone who does is urged to seek medical help immediately.
The theft took place on Worting Road, Basingstoke, between 8.30pm on 29th June and 5.55am on 30th June.
Anyone with information should contact 101 quoting: 44200238349.
Alternatively, you can call Crimestoppers anonymously on 0800 555 111.