"At certain points when we've exhausted all possibilities, that's when we refer it to the coroner."
The case had not yet been referred to the coroner, but the spokesman said it would be.
"Even though we refer to the coroner, it doesn't mean we'll stop investigating, so we'll continue...to work on information we receive."
There had already been extensive searches in the area around Curio Bay, the spokesman said.
"As items were washing up from the car, we did have staff out there looking for anything else that may have potentially washed up."
Locals had told police that other people who had gone missing in the bay had also never been found.
"Unfortunately it's not like this is a one off."
Earlier today Southland Area Commander Inspector Kelvin Lloyd said with the condition of the vehicle, and the conditions of the surf it had been in for the past months, there was a chance police would not be able to locate anything, even if Mike and Mr Beckenridge had been in the car,"
"We have sat down with the family and talked them through the results and outlined the next steps.
"Understandably, they are distraught since they have not been able to find closure regarding this part of the investigation, but we are continuing to provide them with the appropriate support," Mr Lloyd said.
"We are still receiving information from across New Zealand from members of the public which we are thankful for, however we still have had no confirmed sightings of either Mike or John," he said.
"With the fact there have been no confirmed sightings and the results of the forensic examination now being complete, staff will be collating all the information we have which will then be passed onto the coroner."
Michael and his stepfather have been missing since March 13, when the boy was taken during a lunch break from James Hargest College's junior school in Invercargill.
Mr Beckenridge's blue Volkswagen Touareg car was discovered in the water near Curio Bay on March 26.
