A police spokeswoman today said the cash box was still missing and police were searching Cudby Street, opposite the Waterloo bus depot, for the missing box.
Locating the cash box was key in establishing what happened in the lead up to Mr Curry's death, Detective Inspector Darrin Thomson said.
A post mortem examination on Mr Curry's body was carried out yesterday.
"Preliminary results show he did not die as a result of any substantial injuries. Mr Curry's family have been relieved to hear this fact," Mr Thomson said.
Meanwhile Tramways Union national secretary Gary Froggatt said something needed to be done to ensure the safety of bus drivers.
"I think the Government has a responsibility to assess the companies to provide safety and so does the Department of Labour and probably the Accident Compensation Commission; prevention is better than having something happen later on."
There were many incidents around the country where bus drivers were being put at risk.
As a result of Mr Curry's death security at bus depots had been stepped up in the evenings, but Mr Froggatt said more needed to be done.
"I think there should be an urgent conference called by the Government, similar to the taxi industry investigation," he said.
CCTV cameras were not a common feature at bus depots and that would be a cheap way to deter would-be robbers, he said.
Installing CCTV cameras was something NZ Bus should urgently consider.
Bus drivers were also being spoken to following Mr Curry's death to make sure they were aware of their surroundings, Mr Froggatt said.
Yesterday one driver wrote: "Only two weeks ago and a driver had his tin stolen, same area, and it happens often. What has NZ Buses done about it. NOTHING. Maybe now there is a death maybe something will be done."
NZ Bus chief executive Zane Fulljames said there had been a number of incidents where cash boxes had been stolen, but nothing like Friday's attack.
Late last year NZ Bus said it was considering whether to cancel some services after a bus driver was attacked by a passenger.
Curry was a regular late-shift bus driver, who had been working in the Naenae area for about eight years.
Tulipe Tofilau, whose husband worked with Curry, said she did not want her husband to work at night.
"It's not safe now."
Another bus colleague, Tenari Moananu, said he thought Curry was refuelling his bus when he was killed.
