"It is during this struggle that the Taser is believed to have become detached from the officer's belt," Tairawhiti area commander, inspector Sam Aberahama said.
"As soon as the officer realised his Taser was missing, staff retraced their steps and revisited all the places they had been overnight to try and locate it, including a search of the beach during daylight hours."
He said the incident was being taken very seriously.
"We acknowledge the potential risk that could be posed if the Taser ends up in the wrong hands," Aberahama said.
"We are satisfied that we have done everything we can to try and find the Taser, we believe it was lost sometime between 10pm and 12:30am.
"We would like to advise the public that the Taser is a restricted weapon and maintaining possession of it may constitute an offence.
"If you come across it, please call 111 immediately so local Police can recover it safely."
If anyone has seen or knows where the Taser may be, they should call their local police or report anonymously via Crimestoppers on 0800 555 111, police said.
Police have begun a policy, practice and procedure review of the incident.