Mystery surrounds a police operation in Christchurch this morning.

Police were called to an address on Trents Rd, Templeton, at around 6.30am today, police said in a statement - but they're not sure what for.

"Reports from witnesses are varied and police are trying to establish exactly what occurred, some have reported a firearms incident, others a motor vehicle crash," Detective Senior Sergeant Neville Jenkins said.

A number of people who were in the area at the time were being questioned, he said.

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The scene has been cordoned off and a scene examination is being carried out.

The Armed Offenders Squad is also at the scene, and has declared it safe.

"At this stage police are not aware of any injuries but inquiries are under way," Jenkins said.

Trent Rd is expected to remain closed off for the next few hours.

Motorists are being asked to follow the direction of emergency services and expect delays as the operation has closed State Highway One in both directions.

Anyone with information or who was in the area at the time is asked to contact Christchurch police on 03 363 7400 or anonymously contact Crimestoppers on 0800 555 111

- More to come