Three people sustained moderate injuries from a two-car crash on State Highway 1 near Milburn, 51km south of Dunedin.
The crash prompted Milton chief fire officer Alan Tapp to say a large bump in a newly constructed passing lane may have caused the accident.
Mr Tapp said he stood by his comments but declined to comment further when contacted yesterday.
New Zealand Transport Agency (NZTA) coastal Otago area manager Roger Bailey said all fatal or serious injury crashes were subjected to thorough investigations by police and the NZTA.
Those investigations included the road environment, mechanical condition of each vehicle, speed they were travelling, and the behaviour of the driver, he said.
"Until such an investigation is completed into this crash, it is not appropriate to speculate on what may have caused this particular crash."
Mr Bailey said the passing lane construction project was north of the crash site, and had experienced ongoing pavement issues, including rough and undulating areas.
Warning signs were put in place last year to warn road users of the conditions, he said.
The conditions were caused by "unexpectedly high moisture levels" in the clay under the road, and were not a reflection of the contractors who constructed the passing lane, he said.
"A contract has been awarded to strengthen and smooth the pavement and work on this is expected to start next month and be completed before winter."
Senior Constable Darren Cox, of Balclutha, who attended the accident, said it was too early to say what caused the crash, but the area was not considered a "black spot".
"We don't have a lot of accidents around that area."
The 43-year-old female driver and 47-year-old male passenger of the southbound car, which was travelling for a race meeting, and the 59-year-old driver of the northbound car were recovering in Dunedin Hospital, he said.
