Daniel Andrews has been placed in intensive care in hospital where he is expected to remain for "the next few days" after suffering a serious fall this morning.
The Victoria Premier issued a statement via his office this afternoon giving details of the accident and his condition.
"Early this morning, I was admitted to hospital after slipping and falling on wet and slippery stairs," Andrews said. "A CT scan has revealed several broken ribs and vertebrae damage, and subsequent medical advice has recommended I remain in intensive care for the next few days."
Andrews said his wife Catherine and his children were "extremely grateful to the Ambulance Victoria paramedics who showed such care and kindness to our family this morning, as we are to the clinicians who have taken care of me today".
"Our warm and sincere thanks go to the many family members, friends, colleagues and Victorians who have sent messages of love and support throughout the day. Thank you," he said.
"I hope to be able to provide another update later this week. James Merlino will serve as Acting Premier while I recover over the next few days. For now, we'd like to ask that our family's privacy is respected."
Earlier, Andrews' office confirmed he was taken to hospital after falling while getting ready for work.
His office had described the fall as "concerning" but provided no further details on his condition until the afternoon statement from the Premier.
Andrews was forced to back out of an Indigenous Affairs press conference scheduled for this morning.
Deputy Premier James Merlino spoke in his place, telling reporters "only a trip to the hospital" would have stopped Andrews being present.
Merlino started the press conference by addressing Andrews' hospitalisation.
"He took a fall this morning as he was preparing for work," Merlino said.
"He is fine and will be back on his feet very shortly."
State Opposition Leader Michael O'Brien extended his support on Twitter.
"Hope it's not serious," he wrote. "Wishing Daniel a speedy recovery."
Andrews had been on leave for several days and was returning to work today.
His scheduled press conference was to launch an Australian-first inquiry to investigate the ongoing effects of colonisation on the state's Indigenous community, The Age reported earlier.
The "Truth and Justice Commission", similar to one in post-apartheid South Africa, will help guide Victoria's treaty negotiations and potentially explore reparations, according to the newspaper.
It will have the same power to compel witnesses and make recommendations as a royal commission.
Andrews signed off on the inquiry's terms of reference with his Cabinet last week and was due to announce them at this morning's press event.
"I know around the Cabinet table and speaking to Dan privately how passionate he is about this day and about this announcement," Merlino said.
"It would only have been a trip to the hospital that would have kept him away."
Merlino said the work for the inquiry would begin in the coming months.
"From today, we'll have expression of interest for five commissioners that will run," he said.
"This will be an independent commission. It will be at arm's length from government and in line with the calls from the First Peoples assembly, again it will have the powers of a royal commission."
The Deputy Premier described it as "long overdue".
"It's an acknowledgment that the pain in our past is present in the lives of people right now," he said.
"It's a recognition that, without truth, without justice, you can't have a treaty. You can't take that incredibly powerful step forward until we go through this process of truth and justice."
He added, "Indigenous and non-Indigenous people alike (deserve) the opportunity to tell their whole story, for that to be a path to truth and a path to healing. You can't have true reconciliation for all Victorians until we go through this process."