CBC's the fifth estate is following the convoy of trucks carrying Thika, Toka and Iringa to the PAWS Wildlife Sanctuary in San Andreas, Calif., and will be sending live updates throughout the trip.
Producer Lynette Fortune was interviewed Friday on CBC News Network and said the elephants are travelling well.
Their convoy crossed the border early Friday after leaving the zoo just before 11 p.m. ET on Thursday
"I don't think the border agents believed what they were seeing," she reported. "They got out their flashlights and looked at Iringa's foot and as the truck pulled away they said 'be careful with them.'"
Fortune reported that the elephants are "riding very well."
"The goal is to keep them warm and comfy during the journey," she said.
The fifth estate also posted a photo on its blog documenting the elephants' journey, showing the team of handlers installing panels to keep the elephants warm during the trip, which is expected to take about 50 hours.
Several handlers and veterinarians are travelling with the elephants.
Toronto city council voted in 2011 to send the three aging elephants to the PAWS animal sanctuary near Sacramento after animal rights advocates voiced concern for their welfare.
A series of squabbles involving zoo staff, city councillors and animal advocates delayed their departure.
In the end, it was decided to move the elephants to a new home in a warmer climate.
For more than a year, trainers worked with the elephants to prepare them for their move, so that the pachyderms would feel comfortable in their crates when being transported.