More than 400,000 Queensland premises lost power ahead of the afternoon peak on Tuesday. While critical services switched to backup generation, industrial users, including the Boyne Smelters at Gladstone, bore the brunt of the economic impact as authorities asked Queenslanders to conserve power.

Traffic lights went off around south-east Queensland, some businesses sent workers home, while on the Gold Coast nine people were reportedly stuck in an elevator on the 53rd floor and had to take the stairs down.

The loss of supply from Callide initially knocked other generators offline and led to hours of uncertainty, during which time wind power hit capacity and pumped hydro had to be switched on to avoid the need for load shedding.

But parliament was told this morning the still unexplained Callide fire – which has left a multi-million dollar hole in the state’s power network – could have been deadly.

Of the 236 workers at the plant near Biloela, which is an hour and a half from Gladstone, only three were trained as stand-by firefighters. They did what they could until dozens more Queensland Fire and Rescue Service members arrived with equipment to fight the blaze and enforce a 550 metre safety cordon.

“Thankfully, no-one was hurt,” Premier Annastacia Palaszczuk told parliament.

Health Minister Yvette D’Ath praised emergency services workers who she revealed were responding to a “potential mass casualty event”. 

There were reports of explosions and the fire took hours to bring under control. The site was returned to CS Energy around midnight on Tuesday, allowing for an assessment of what can be salvaged. An investigation will determine the cause of the fire, which will constrain Queensland’s generation capacity for months.

CS Energy CEO Andrew Bills said he was relieved noone had been injured or killed in the incident.

“I have already spoken to some of our people and will be talking to the Callide workforce this morning to check in on how they are going and to see firsthand the response to the incident,” Bills said.

Initial information suggests the fire in the turbine hall for Callide C4 caused extensive damage and will require the turbine to be replaced. Three other units in that generator may be salvageable.

Asked by the Opposition whether the dividends paid by CS Energy to the government left Callide exposed to faults, Energy Minister Mick de Brenni said any maintenance work that was required was done and paid for.

“We’ve been making sure we invest in them,” de Brenni told parliament, pointing to $324 million being spent on Callide C alone in recent years.

One of the Callide generators was offline for maintenance, and renewable supply fluctuates, prompting the Opposition to ask whether generators were being worked harder to compensate. Minister de Brenni said “it is too early to tell what the cause of this unprecedented incident was” but an investigation had started.

He said by diversifying supply, and not privatising power assets, the Labor government had made the network more resilient and responsive.

Had the incident occurred in summer, under higher demand, there would have been even greater disruption. Over summer in 2004-05, blackouts led to an inquiry that found there had been insufficient investment in the distribution network, causing it to fail under pressure. Networks are now being driven harder, again, in an effort to keep power prices down.