A number of canisters stolen from a motel in the Auckland suburb of Ellerslie contain hazardous calibration gas, police warn.
They are investigating the burglary which happened between Thursday evening and early Friday morning last week.
The heavy cylinders targeted by thieves contain gas substances that can affect breathing and cause eye irritation.
Seven were taken and there wasn't "extensive" damage to the motel, police told the Herald, making it seem like an opportunistic break-in.
"We believe other items have been stolen but are working through this," a spokesperson said.
Police urge anyone who may find the cylinders to avoid touching them and to call 111 immediately.
Anyone with information is asked to contact 105, quoting 210507/7439 or Crimestoppers anonymously on 0800 555 111.