It's been nearly five days since five-year-old Leonine O’Driscoll-Zak and two-year-old Wyatt O’Driscoll-Zak were last seen.
And their father is pleading with anyone who has details about their whereabouts to provide information to help bring them home.
The girls were last seen at their home in rural Cochrane on Friday, March 12 at around 9:30 am.
Their father, Colin Zak says it's been an arduous time.
"It's been a really difficult past couple of days, it's been a difficult number of months. We've been working through the courts, taking all the right steps to get these girls into a safer situation and then this happens at the last minute."
Zak was ordered full custody of the girls but when he went to go pick them up they were gone.
The disappearance of the children is being investigated as an abduction, and the girls are suspected to be with their grandmother 68-year-old Therese O'Driscoll and aunt, 38-year-old Alison O'Driscoll.
Zak says "It's been devastating. This is a family I've known for the better part of a decade and a lot people in Cochrane know this family as well and I'm just so devastated that this has happened."
There's specific criteria that must be met in order to activate an Amber Alert and in this case the RCMP say "they do not have evidence to indicate that the threshold has been met."
However, Zak disagrees. "They say that the children aren't in danger but the court disagrees. That's why the court ordered the immediate removal of the children. That's why the court-appointed psychologist was supportive of that. It's a dangerous game of semantics when you start having RCMP disagreeing with the judgement and disagreeing with the experts who are actually familiar with this case."
He worries for the safety of his daughters.
"I'm very concerned. The mother is extremely unwell. The mother of my children is extremely unwell. That's why the court has ordered a psychiatric assessment and that's why they removed the children ultimately. I think that's what it comes down to."
Zak is pleading with anyone who has any information on the whereabouts of his girls and is urging them to call 911 if they know anything related to their disappearance.
He says he just wants them home and safe again.
"Hold them in my arms and keep them safe and just let the time for healing begin."
CochraneNow has tried to be in contact with the mother and the mother's family but has not been successful.
If you have any information in relation to their current whereabouts, you are urged to contact the Cochrane RCMP and if you wish to remain anonymous you can call Crime Stoppers.
You can listen to the interview with Colin Zak below.