Communities were not warned that they were in the path of a Black Saturday firestorm, despite authorities having known for hours that the blaze was out of control, a court has heard.

The CFA, Victoria Police and environment department knew by 12.30pm that a blaze sparked at Kilmore East at 11.45am on February 7, 2009, was out of control and moving southeast at rapid speeds, Jonathan Beach QC told the Victorian Supreme Court on Wednesday.

Some communities, like St Andrews and Steels Creek, were never warned that the blaze was headed straight for them.

Other communities, like Kinglake, were warned after the blaze had already swept through and claimed lives, the court heard.

Carol Matthews' 22-year-old son Sam was at his St Andrews home constantly monitoring the CFA website for updates on February 7, 2009.

He had no idea he was in danger until his home was engulfed and he was incinerated inside, the court was told this week.

Mrs Matthews is leading a class action of more than 10,000 members, suing SPI Electricity for compensation, alleging its negligence in failing to maintain its power lines had sparked the Kilmore East blaze that killed 119 people, including her son.

She is also suing Victoria Police, the CFA and Department of Sustainability and Environment (DSE) for failing to warn people of the blaze.

SPI is defending the allegations but is also joining the plaintiff's action against the state entities for their failure to warn people.

Mr Beach, for SPI, said people were already dead in several communities before alerts were published on the CFA website.

The blaze hit the community of Upper Plenty at 3.11pm but the CFA did not publish warnings until 4.40pm, by which time two people had already died.

It hit Humevale at 3.55pm and killed six people but warnings were not published until one hour later, on the DSE, not the CFA, website, he said.

"They were too little and too late," Mr Beach said.

The CFA, DSE and Victoria Police deny the allegations and are defending the claims.

Mr Beach said the case was directed at the entities and the flow of information, rather than at individual officers.

"We're not making any criticism of any CFA or DSE personnel or Victoria Police," he told Justice Jack Forrest.

Mr Beach said the Victorian Bushfire Line also failed to provide information, with 82 per cent of callers, or 8125 people, abandoning their calls before they were answered.

Only 1754 were actually answered, he said.

"That indicates that that line was significantly overburdened and did not operate at all well on the day," he said.