A man has been arrested and more than 20,000 canisters of Nitrous Oxide seized after police raided a premises in Fallowfield.
Officers said they obtained a warrant to search the property after a tip-off.
And the Fallowfield Neighbourhood Policing Team shared images of what they found on their Facebook page.
Nitrous Oxide, sometimes known as laughing gas or 'Noz', is a colourless gas that has many uses including boosting motor engines and aerosols.
It is also used by medics as an anaesthetic and for pain relief and in recent years has become a popular recreational drug.
The gas is usually inhaled via balloons and gives users a brief euphoric feeling.
However, the abuse of Nitrous Oxide has proven very dangerous and is increasingly become a police matter.
Experts warn it can cause serious side effects including falling unconscious due to a lack of oxygen reaching the brain.
The Office for National Statistics states the inhalation of Nitrous Oxide was linked to 25 deaths between 2010 and 2016.
Legislation introduced in 2016 made it illegal to sell the gas for psychoactive purposes.
In their Facebook post, GMP said a man has been arrested an investigations continue.
A notice pinned up in the premises added: "Following an intelligence lead policing operation, your Fallowfield Neighbourhood Policing Team have obtained a warrant under the Psychoactive Substances Act 2016 issued by Manchester and Salford Magistrates Court.
"The aim is to search this property, in its entirety, primarily for evidence to suggest that this establishment, its management and staff, are illegally supplying Nitrous Oxide canisters and other related paraphernalia to the general public.
"On display of this notice confirms that such evidence has been located and seized, and that a criminal investigation has commenced by Greater Manchester Police and their multi-agency partners.
"Further information on this investigation will be released in due course.
"To inform Greater Manchester police of any suspected criminal activity in your area please telephone GMP on '101' or Crimestoppers anonymously on 0800 555 111."