The NSW police drug squad said the light blue tablets stamped with a batman logo were being sold as a form of ecstasy but contained "dangerous levels" of 25c-NBOMe, a synthetic, LSD-type substance that caused psychotic behaviour.

Last weekend, five teenagers in the Hawkesbury area of Sydney were reportedly hospitalised after taking Blue Batman at a house party.

But drug squad commander Detective Superintendent Tony Cooke said there had been cases in Australia and abroad where people affected by the NBOMe class of drug had died.

"We are aware of the Blue Batman pills and, in particular, a number of bad reactions users had after taking them at an event in the Hawkesbury last weekend," he said in a statement.

"In fact, similar pills recently seized by police contained the drug 25c-NBOMe, one of the so called new psychoactive substances recently outlawed. A closely related substance was in fact involved in the death of a young man in Sydney last year."

Henry Kwan, 17, jumped to his death at Killara, on Sydney's north shore, last year after ingesting a tab of the synthetic substances. He is believed to have allegedly bought the drug from a classmate who told him it was LSD.

His father, Stephen Kwan, said his son had removed his clothes and said he "wanted to fly" before he jumped.

In January, a "bad batch" of ecstasy pills, including Blue Batman, put 21 people in hospital around Perth and prompted a similar warning from Western Australian police at the time.

NSW banned a range of synthetic drugs in October last year. "The reality is there is no quality control in the production of illicit drugs. You just do not know what you are taking," Detective Superintendent Cooke said.

"Illicit drugs are produced in filthy backyard laboratories by criminals with absolutely no interest other than making money," he said.

"The health and well-being of their customer base is simply not a priority."