Canterbury Coastguard services were called in to rescue eight people stuck atop two cars stuck in the Waimakariri River.
Police were called to the scene just after 4pm, with reports that two cars were stuck in the river and their occupants had escaped to the car roofs.
Police said all of the occupants were reportedly out of both vehicles and back on land.
St John ambulance crews also attended the incident, though it was unclear if there were patients needing medical help.
South Island region spokesman Gerard Campbell believed eight people had been in the two cars and had been awaiting help atop their vehicles.
"It looks like coastguard is picking them up from the river in inflatables."
Campbell didn't know how the cars ended up in the river.