Police say tests for the unknown substance thown at officers during the anti-mandate occupation on Parliament grounds have come back inconclusive.
Three officers were treated by paramedics and then taken to hospital for a medical assessment after being sprayed with a stinging liquid substance at the Parliament protest on February 22.
Wellington District Commander Corrie Parnell says two separate labs analysed material from vests worn by staff, but had no positive results for anything that could have caused the burning sensation.
"At the scene, all members were heavily washed down with a water and baking soda solution which likely washed away any evidence or form of a chemical substance."
Police say there were "a variety of liquid substances" at the protest at the time, including pepper spray.
Police said they are continuing to investigate the incident and other possible criminal behaviour related to the protest.
