A post-mortem on a Hamilton woman who collapsed while being breathalysed shows she probably died of natural causes, according to police.
Elizabeth Jill Gilbertson was stopped near a routine police alcohol checkpoint on Cambridge Road in the suburb of Hillcrest about 10.15pm on Sunday.
Police say the 56-year-old failed a roadside breath screening test so was required to complete an evidential breath test in a police 'booze bus'.
They say the woman collapsed and fell from her chair during the procedure and appeared to need assistance.
Despite immediate first aid and treatment from paramedics, she died at the scene.
Detective Inspector Chris Page says he is confident that the officers acted appropriately.
"I'm quite comfortable that the police involved in this instance did everything right, did everything that they should have.
"They're involved in a team whose job it is to prevent deaths and save lives, and that's what they tried to do with this lady. It's a tragedy, really, that she died in their arms."
Mr Page says indications from the post-mortem carried out on Monday morning show that Ms Gilbertson died of natural causes, but the exact cause of death is yet to be determined.
The death has shocked and upset the Gilbertson family and the officers involved, he says.
Police will conduct an inquiry and will notify the Independent Police Conduct Authority. The death has been reported to the Coroner.