A dangerous substance linked to deaths in the North Island has landed eight people in Christchurch Hospital

A number of people suffering from probable severe synthetic cannabis toxicity presented over a 24 hour period - with three admitted to the Intensive Care Unit.

Emergency Medicine Specialist Paul Gee says symptoms can range from minor adverse effects, to cardiac arrest.

He says the substance taken by the patients was either AMB-FUBINACA or AB-FUBINACA, which are inked to numerous deaths over the past year.

Dr Gee says patients weren't able to give any information to identify what they had taken - so all synthetic cannabis should be considered dangerous.