Pacific Memorials co-owner Carina Zhang said the body had fallen out as it was being transported by the firm. She said the driver of the hearse had reported Tuesday's incident to her but she was unsure how it had happened. However, early indications were a faulty latch on the rear door was to blame.
The corpse had been inspected immediately and was unharmed, but the family of the deceased had not been told of the incident, said Ms Zhang.
One man, who wished not to be named, was stopped in his car at the intersection when he saw the hearse take off at the lights.
"I was just parked there and all of a sudden I saw the funeral car's boot open and something slipping out and it was a body."
The man took a photo of the incident on this phone, capturing an image of the hearse driver and a motorist trying to put the body back into the hearse in the pouring rain.
"I was about three cars back and saw it falling out. The driver had no idea and when he moved the vehicle to take off it just rolled back and the back opened."
Motorist Alison Smith said she pulled up at the intersection about 1pm to see the body "lying on a gurney in the middle of the road behind the hearse".
"It was quite surreal, really, but because there were no cops and nothing appeared to have happened, I thought, 'Why is there a dead person on a gurney in the middle of the intersection?'
"The gurney - the wheels had collapsed, so it was just somebody lying in the middle of the road, in the rain.
"I was just thinking, if that was a member of my family, that would be so disturbing." The incident had blocked traffic flow and some motorists were quick to help, said Ms Smith.
"The funeral director was parked about a third of the way across the intersection ... The guy in the car behind had got out and they were trying to get the gurney back in, but the boot kept closing on the hearse."
A teenage passenger from another vehicle also helped, Smith said.
"This really not much more than a kid, teenager, got out and held up the boot of the hearse so they could put the gurney back on."
Bobby Boskovic, who works at the nearby Manukau Park and Sell car-sales business, said he and his co-workers also saw the incident unfold.
"I just saw what looked like a body going back into a hearse ... I've seen lots of different things; nothing like that, though.
"I wasn't sure what the hell it was, but it looked like a body on a gurney."
Boskovic's employee Amber Neale also saw the event unfold.
"It took us a while to comprehend or come to terms with what we were seeing," she said.
"It was one of those trolleys they have in the back of ambulances and when the wind stopped blowing the sheet and it was still, you could see the outline of a person lying down."
Neale said the incident probably happened in the space of about two minutes.
"But when you think about it, and in the pouring rain, that's quite a long time."
Zhang said the incident was "unfortunate" but the company had done everything it could to prevent it recurring.
"It was a really bad accident. The driver involved really was shocked. The body was okay; nothing happened to it. It was really a very unfortunate accident. We do feel so bad."
The hearse was being repaired, Zhang said. "We are having the vehicle checked today [Wednesday] and trying to fix it. It's the latch on the back, they said."
Funeral Directors Association of New Zealand chief executive Katrina Shanks said Pacific Memorials was not one of its 100-plus accredited members.
"Unfortunately, there are operational failures on occasion and it sounds like this is one of those situations. It's extremely upsetting for the family for something like this to happen and my expectation will be that the funeral director is doing everything it can to make it easier for the family."
Shanks, a former National MP, said the industry was not currently regulated, but a report by the Law Commission was due to be completed in October that might introduce legal operational standards.
The incident was not reported to the police.
'Understanding' family accepts apology
Zhang said that she contacted the family of the body, that was being transferred from a hospital to the funeral home.
"We have contacted the family and apologised and they have been really wonderful. They expressed their understanding and they accepted our apology.
"We also contacted some families that we are going to serve in this coming week whose funeral might under the influence of this news.
"So far all our families are very generous and understanding."
The vehicle had now been fixed, she said.
"We also want to apologise through the newspaper to the publicise, especially those people involved on the scene. I believe it might be a horrible scene for them to see and also to the general public who might be offended by something like this."
Zhang said the hearse's driver was very upset by the incident and was being supported by the company.
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