UPDATE 1.40pm: A paramedic radio outage is not causing public safety issues, according to Ambulance Victoria and the Emergency Services Telecommunications Authority.
ESTA head of corporate affairs Rosie Mullaly said job information was still getting through to paramedics.
"The primary system is the paging," she said.
"They're using an alternative radio channel or system.
"But absolutely, the service is still operating.
"There is no impact on anyone calling Triple-0 and no impact on us dispatching jobs."
Ms Mullaly said the ambulance union was using the issue in its long-running battle with the government over wages.
"For the union to raise this to frighten the community around the operation of the Triple-0 service is just irresponsible," she said.
Ms Mullaly said she had heard a cable had been cut, blacking out radio access in northern Victoria, but could not confirm that.
An Ambulance Victoria spokesman confirmed paramedics were still receiving job information.
UPDATE NOON: Radio broadcasts to paramedics are still unavailable, according to ambulance union secretary Steve McGhie.
Mr McGhie said new information showed the system had gone offline at 11am and was still not working.
"I've just been informed it is still down," he said.
"I've been told there's no redundancy provision.
"They're using an old base radio that they've plugged into a power point and they're talking to ambulances as if talking car-to-car.
"It does cause delays in response times, but at this stage there's been no adverse outcomes with cases."
Mr McGhie said while there was a pager system in place for back up use, it was less effective than radio transmissions.
"They can only receive a page," he said.
"It's only one-way communication.
"Paramedics can't ask questions via the pager or send back any updates."
EARLIER: Bendigo paramedics were cut off from emergency radio broadcasts for almost half an hour today, according to the ambulance union.
Ambulance Employees Australia of Victoria secretary Steve McGhie said a local paramedic had alerted him to a communications blackout.
A photo of a pager shows the issue was raised at 11.27am.
Mr McGhie said the radios were back online at 11.53am.
“It could have impacted on some cases,” he said.
“It depends on how many emergency cases went off in that time.
“It shows if the radio system goes down, there’s no other way of verbally communicating to ambulance crews.”
The union and state government are currently in wage discussions, but Mr McGhie said the issues were not related.
“It has nothing to do with the EBA,” he said.
“This is a system in crisis.
“This is about another communications issue that puts paramedics and the public at risk.
“The system has gone down several times in the last six months.”
He said paramedics had had to rely on their personal mobile phones for verbal information, but said they weren't required to carry phones.
They also use a paging system to receive information.
Ambulance Victoria has been contacted for comment.