St John stood down from the incident at 2.55pm.
The Herald understands several children were among the groups stuck in the carriages.
Police were unsure how many people had been trapped in total.
Two ambulances have been at the scene assessing people getting off the cars.
Toni Peel, of Greymouth, was one of the passengers trapped in the swinging cabins and said she was "a basketcase".
She said after being stopped for 15 minutes, she phoned the Christchurch Gondola office and someone told her they were getting an engineer and that they were getting them down as quickly as they could.
"We sat up there for about an hour then we started moving forward a couple of metres then stop, then back a couple of meters then stop. We did that on and off for about an hour then they got us off. Two hours in total we were stuck on there," she told One News.
Mrs Peel said as soon as they got to the top, they were handed bottles of water.
"But it was hot, hot as. There was no air conditioning."
And then when they got to the top, they had to face going back down on the same gondola because it was reopened once the fault was identified.
Passenger Jane Scott said although there were windows, it was "really, really hot" in her cabin which stopped over the road.
Ms Scott said she also grew frustrated at the lack of communication because she had to call the shop three times, who then put her onto the operator but no one really had any information.
Christchurch Gondola managing director Mike Esposito said the incident was a technical fault on a safety mechanism on one of the 18 cabins.
As a precaution the cabin had been taken off the line for testing, he said.
Mr Esposito said the technical grip fault happened every once and a while, saying the company followed daily, weekly and monthly checks that were independently audited by SGS, the world's leading inspection, verification, testing and certification company.
"There was never any danger to passengers," Mr Esposito said.
He believed there were between 20 and 30 passengers on the gondola when the incident occurred in sunny conditions. Passengers were offered refunds on their $28 tickets.
The gondola has been operating since 1993 and carries 150,000 people a year.
Mr Esposito said there had never been an accident on the popular tourist attraction.
The gondola ride goes about 1km to the top of the Port Hills, almost 500 metres above sea level.
It is one of the must-do tourist attractions in Christchurch.
"You will never forget your Gondola experience," the company said on its website.
