High Alert, an organisation that provides early warnings about dangerous drugs in the community, and Canterbury police warned people about the batch of the drug on Thursday.
"We recommend extreme caution consuming synthetic cannabinoids, especially in the Canterbury region at this time," High Alert said.
The drug is likely present throughout Canterbury and possibly in other regions across New Zealand too.
High Alert said the batch may have caused at least two serious hospitalisations in Christchurch within a 24-hour period last week.
They advised caution when consuming all synthetic cannabinoids as it is not yet known which one is responsible for this harm.
"This is being investigated. We will provide updates on this when more information becomes available."
The appearance of the drug is described as yellow/brown. The active ingredient is a powder that is dissolved and sprayed onto dehydrated plant material, which is then smoked.
It often has a chemical smell and it may be sticky, making it noticeably different from cannabis.
High Alert warns that synthetic cannabinoids can vary in strength.
"This makes it harder to predict how strong the effects will be, even when using synthetic cannabinoids from the same bag."
"People may collapse or 'drop', foam at the mouth, or experience temporary paralysis.
"The effects are often worse if taken at the same time as alcohol and other drugs, if a person is unwell, or experiencing mental distress."
Users are advised to only use small amounts, ensure that someone sober is with them and place themselves in a safe position before usage, such as sitting down.
High Alert advises users to call 111 if they or someone else shows signs of overdose, such as extreme agitation, no breathing, seizures and/or unconsciousness.
More information about the drug is available here. You can report your non-emergency experience or any unusual effects from the drug here.
