The cremation of a 230-kilogram body caused foul-smelling black smoke to billow out of a Christchurch crematorium for five minutes on Wednesday.
Rod Stuart, who runs a business 50 metres from the Sydenham Crematorium, said the black smoke caused an unpleasant odour.
A handful of people who gathered on the street to watch the smoke pour from the chimney were shocked when crematorium owner John Guthrey came out to apologise.
"He came out and told everyone, 'The body was too big, sorry'," Stuart said.
Guthrey said there had been a "little bit of a glitch".
Once Guthrey realised something was wrong, he phoned the Auckland manufacturer of the cremator to ask for help, and also Environment Canterbury (ECan).
He altered the cremator and the smoke stopped within five minutes to allow a "successful cremation from there".
"We have got no excuses. We apologised to the people in the area and all I can say is it won't happen again."
Guthrey said he would inform the cremated man's family about the incident.
The crematorium had been operating for four months without a hitch, Guthrey said, and the incident was "unfortunate".
He was told by the manufacturers to cremate "very large bodies" first thing in the morning when the unit was still cold.
The Sydenham Crematorium was granted non-notified consent by Christchurch City Council and ECan, despite community and business opposition.
"I am very aware the people in the area don't like what we are doing, so we are trying to do everything absolutely perfectly."
ECan said the crematorium had taken "all the right actions".