The Drug Foundation is labelling a new street drug a killer.

One person is critical in Christchurch Hospital after taking it - and five others have been treated in the emergency department in the past week.

The drug is synthetically produced...it's commonly known as 'N-Bomb'.

Drug Foundation chief Ross Bell said it's potentially lethal, because it's much stronger than LSD.

He said the substance has what's known as a steep-dose response curve - where one drop might be okay but two or three will get you into trouble.

Christchurch Police want help finding the manufacturer, they're asking people with information to call Crimestoppers on 0800 555 111.

Detective Senior Sergeant Jason Stewart said people are taking a huge gamble when they take the drug.

"It's obviously a big concern for the community and for police, the fact that people using synthetic cannabis often don't know exactly what they're taking. They're putting themselves at extreme risk of serious health problems, medical complications and there's even cases overseas of death."

Detective Senior Sergeant Stewart said users are taking a serious risk, and is appealing to the public for information on those dealing the drug.

"It's illegal, so it's sold ... through a black market or illegal groups. Anyone with any information about dealing or people distributing these type of items, we'd really urge them to call the police."