TORONTO -- Wrangling over the transfer of three aging elephants from the Toronto Zoo to a wildlife sanctuary in California persisted Tuesday with each side blaming the other for the problems that have delayed the move for nearly a year.

Zoo officials said there has been "much progress" in the arrangements to send Iringa, Toka and Thika to the PAWS sanctuary, but warned they could not sign off on the plan until "several serious concerns" were allayed, particularly when it comes to the risk of infectious disease at the facility.

"We hope that we can get the required outstanding information to complete our due diligence," CEO John Tracogna said at a news conference.

A representative for PAWS, however, accused the zoo of using scare tactics to stall the deal, which has the support of Toronto City Council.

The holdup divided councillors on the zoo's board, with at least one suggesting the city should reconsider its decision when the matter returns to council next month.

None of those involved could say when the elephants might head to their new home, though some suggested it was unlikely the trio would make the trek in the winter.

But zoo officials were quick to dismiss allegations they were deliberately derailing the project in order to keep the elephants.

"The elephants were going to be going to a new facility regardless, whether that's in California or in Florida or wherever," said senior veterinarian Graham Crawshaw.

"We just want to make sure they're going to a place that's the best for them and up to this time, we haven't been convinced PAWS is the best place."

The zoo attributed its decision to once again postpone the transfer Tuesday to issues with permits, flight arrangements and crate training as well as lingering concerns over the risk of tuberculosis at the U.S. facility.

"Our concerns about the biosecurity of the PAWS facility and the existence of TB are new information" that came to light after the zoo board and city council approved the move, Tracogna said.

He added PAWS has not responded to the zoo's request for additional medical information in a "sufficient and professional manner."

Julie Woodyer of Zoocheck Canada, which represents PAWS, said the facility has been completely transparent about its procedures for dealing with tuberculosis, including a current case of the disease.

She said the organization has bent over backwards to meet the zoo's requirements since the plan was hatched last year.

"I've been hearing a lot of the same stuff for 11 months," she said following Tuesday's announcement.

"It's just a new series of obstacles -- I'm not surprised by it," she said.

Toronto City Council voted last fall to send the three elephants to the U.S. facility after groups voiced concern about the animals' welfare.

Animal activist Bob Barker has promised to pay $880,000 for a plane to fly the elephants to their new home.

Controversy over the elephants' fate cost the zoo its accreditation by the Association of Zoos and Aquariums this spring for the first time in 30 years.

Tracogna has said the key issue in that decision was governance and had nothing to do with its care of animals.