A scene examination is ongoing on the stretch of road, which was closed, and motorists were being thanked for their patience and cooperation while the disruption persists.
Anyone with information relating to the case is asked to call police on 105 and quote file number 200806/1185.
Locals have reported on social media hearing gunshots and of police cars travelling at speed down Paeroa Kopu Rd, south of Thames, shortly after 8pm.
Others reported they'd seen police cars driving along Hayward Rd in nearby Ngatea.
Waka Kotahi NZ Transport Agency has closed SH25A between Kopu and Hikuai in both directions due to the incident.
The highway was closed from 8.11pm and is expected to remain closed until late afternoon today.
Motorists are advised to take the detour route on SH25 through Coromandel or Whangamatā.