UPDATE 10.10am

Two people died — one after waiting 30 minutes for an ambulance — as hundreds of calls for help hit Melbourne’s emergency services during a so-called “thunderstorm asthma” event.

Ambulance Victoria’s Mick Stephenson confirmed two people died as paramedics dealt with a six-fold increase in calls on Monday night.

“Whether or not they (the deaths) are related to this phenomenon we just don’t know … we will have to review each incident,” Mr Stephenson told reporters on Tuesday morning.

The two people who died had reported respiratory issues, authorities said.

Fairfax Media reported that one of the victims had died after waiting half an hour for an ambulance. The other, it reported, was a 20-year-old who had also died while waiting for an ambulance.

EARLIER

A phenomenon called “thunderstorm asthma” has caused a huge spike in calls to Ambulance Victoria on Monday in the space of just a few hours.

Ambulance Victoria’s Mick Stephenson on Tuesday morning confirmed the deaths. Photo: AAP.

A severe weather change at about 6pm brought with it thunderstorms, rain and strong winds that churned up pollen, dust and other irritants in the air.

Ambulance Victoria’s State Health Commander Paul Holman said every available ambulance had been dispatched and more than 190 cases were waiting during the worst of it.

“I think a spike in calls would be the understatement of a century.”

Paramedics called in help from the MFB, police and doctors to help with the demand.

“These were quite sick patients,” Mr Holman said, saying most jobs were code ones or top priority emergencies.

On a normal night, there would be about 10-20 cases waiting mostly of low or middle priority level.

Extra staff were put on the emergency triage phone service to make sure all patients were spoken to see if they needed an ambulance or could instead go to their local GP, Mr Holman said.

By 10.30pm, about 90 cases were still waiting, but they were of lower priority.

Mr Holman said it had been an “unprecedented phenomena”.

“It’s something in my 40 years I’ve never seen before,” he said.

He expects most of the cases to be dealt with by midnight on Monday.

The State Emergency Service (SES) is still responding to hundreds of calls for assistance, including for property damage.

https://twitter.com/ScottBarkerAU/status/800604166032912388

Altona Meadows resident Marie Clement has lost all the tiles from a section of her roof.

“The noise was unbelievable, it was truly unbelievable,” he said.

“The chairs were shooting past the family room window, the garden chairs — it was very frightening indeed.”

– AAP