An elderly couple killed after a truck veered off a "dead straight" road and slammed into a house had spent their lives devoted to family, their devastated relatives say.
Jim Madden, 81, and wife Carmel, 80, were at home in Tower Hill in Victoria's south west when the truck veered off the Princes Highway and crashed into their property just after 7am on Friday.
Footage from the scene shows the truck crashed through a paddock, into a fence and down one side of the house before collecting part of the roof.
The truck driver, a 70-year-old Portland man, suffered non-life threatening injuries and was taken to hospital for treatment.
The couple's family said they are totally devastated by the tragic events on Friday morning.
"Jim and Carmel devoted their life to their family and have given us all so many opportunities and were immensely proud of us all," they said in a statement.
"As hard as it may be for everyone, they would want us and all their valued friends, the Tower Hill and Koroit communities, and all those in the farming and racing industry to continue on working to make the world a better place."
Detective Sergeant Stephen Hill said the cause of the crash was under investigation.
"We're keeping an open mind as to what was going on," he told reporters at the scene on Friday.
"Whether it's a mechanical fault with the truck, whether there's a medical episode involved, whether it's inattention, whether it's phone use involved, all those things will have to be looked at in the next few days."
He described the section of the road as "dead straight" and said there would be no reason for vehicles to swerve unless they were overtaking.
Local business owner Richard Crawley said the victims were farmers with many family connections to the area and he expected the crash to affect the community.
"It will have a big impact, Jim and Carmel Madden were very well-known people," Mr Crawley told AAP.
About 100 people live in the Tower Hill area, according to the 2021 census.
Mr Crawley said he drove near the house in the hours after the crash, before he was diverted away.
"It's sort of hard to fathom what actually has happened, because it doesn't make any sense at all that a bloody great big B-double truck on a dead straight part of the highway can do what it did," he said.
Detectives from the Major Collision Unit have travelled about three hours from Melbourne to the scene to investigate.
Anyone with information about what happened or relevant footage is urged to contact police.
