Five people were hospitalised after taking green pills believed to be ecstasy - prompting a warning from health officials and police.
Three patients were admitted to Christchurch Hospital on Saturday night and one remained there on Tuesday. Two others were assessed, treated, and discharged on Saturday night.
The Canterbury District Health Board did not have any samples or information about the pills taken, other than the patients saying they were green.
Christchurch Hospital emergency department clinical director Dr David Richards said they appeared to have taken MDMA/ecstasy.
He said their symptoms varied but included fast heart rates, hallucinations, agitation and sweating, similar to symptoms a group were treated for in February.
Thirteen people were hospitalised after taking class C drug N-Ethylpentylone after the Electric Avenue music festival in Hagley Park on February 24.
In January, KnowYourStuffNZ issued a warning about three pressed pills that had come onto the market which could contain high doses of MDMA. One was a green gucci, a green pill stamped with a Gucci logo.
Detective Senior Sergeant Sarah Illingworth said police were not specifically aware of green pressed pills, but there were a number in circulation purporting to be MDMA or party pills.
"Christchurch police were not aware of the hospitalisation of five people at the weekend as a result of a reported drug overdose, and are concerned about such admissions."
Detective Senior Sergeant Illingworth said dealers had no idea of the potency of what they were supplying nor what they contained, or simply "do not care".
"End users are unable to tell what is in any pill they take, so put themselves at risk of serious harm or death by buying and ingesting 'party pills', MDMA/ecstasy or synthetic drugs."
KnowYourStuffNZ director Wendy Allison said it was hard to say whether the pills taken would have been green guccis without testing.
She said it was common for pills to have higher dosages than expected, and people needed to approach them with extreme caution.
Dr Richards' advice to anyone considering taking unknown pills was: "don't do it".
However, he said alcohol was a more readily available and acceptable drug, and the ED saw the harm it caused every day.
"Weekends are worse when more intoxicated people harm themselves and others at home, when they are out socialising in town, and on the roads."