Police are warning Christmas revellers to be alert after two women had their drinks spiked.
In separate incidents in Palmerston North over the past three weeks, the women drank small amounts of alcohol but suffered the effects of drink spiking.
Symptoms included feeling light-headed or dizzy, memory loss, numbness, feeling unwell and, in one case, being violently ill the next day.
"It only takes a second to drop a pill, some powder or a few drops of liquid into a drink," said Manawatu adult sexual assault squad head Detective Sergeant Gary Milligan. "The effects of these drugs can start in 10-20 minutes, making a person sleepy, dizzy, uninhibited, relaxed and open to suggestion. This is when women are at risk of rape and sexual assault."
Mr Milligan said the incidents were relatively unusual, although it was likely that some cases of drink spiking went unreported.