A major highway has been criticised as "not up to standard" after three women died in a bus crash.
The bus collided with a caravan being towed by a four-wheel drive on the Bruce Highway in the Whitsundays region of north Queensland on Sunday morning.
Police have confirmed a 56-year-old Townsville woman died in the crash. She is believed to have been travelling with her daughter, who was not injured, from Brisbane to Townsville.
Two women, aged in their 20s and 30s, were also killed in the collision near Gumlu south of Townsville.
Two men, aged 24 and 23, are in critical condition at a Townsville hospital.
They were all among the 33 people on the Greyhound bus that crashed in a 100km/hr zone.
"I want to express my sympathies to those affected by that awful bus crash," Queensland Premier Steven Miles said on Monday.
"I'm sure every single Queenslander is thinking of the families of those who have died, those who are currently being treated at our hospitals and our first responders who I'm told arrived to just awful scenes."
But Opposition Leader David Crisafulli raised safety concerns about the Bruce Highway, with the crash reportedly marking the third major incident in a fortnight.
"There needs to be a proper plan that ensures that we work towards fixing that road," he told reporters.
"It's not up to standard. I don't believe there's a Queenslander who thinks it is."
The area of the highway where the bus crashed could be challenging for drivers, Whitsunday Regional Council Mayor Ry Collins said.
"If you are to drive the road it doesn't feel like a highway, it feels like a country road," he told ABC Radio.
Police said road conditions would form part of the investigation.
"An incident of this nature is very complex so we want to go through that holistic investigation before we really move towards looking at exactly why and how it's occurred," Superintendent Graeme Paine told ABC TV.
Mr Miles said it was too early to speculate about the crash.
"Our investigators will do what they do best and that is identify what exactly has happened here," he said when asked about the state of the highway.
"I wouldn't get too far ahead of ourselves in terms of speculating about this one incident."
Police said the bus and 4WD had been travelling in opposite directions before the collision, describing the scene as "very confronting".
Paramedics treated 27 people, with seven initially taken to a Townsville hospital.
Four people remain in hospital including the two men in their 20s who are in intensive care.
Two men, aged 27 and 51, are in a stable condition.
Medical staff acted quickly after notifying the community to only attend the Townsville hospital if their matter was urgent, acting Chief Medical Officer Jason Yates said.
"We were expecting a mass casualty event and we needed to be ready to respond," he told reporters on Monday.
"Our teams worked really hard. We were able to mobilise additional ...staff who all came in on a long weekend to do their thing."
Greyhound Australia said it was "heartbroken" by the tragic incident.
"Our deepest sympathies go out to those involved and their families and friends," it said in a statement.
Both lanes of the Bruce Highway were eventually reopened to traffic after midnight on Monday, more than 12 hours after the fatal crash.
