TORONTO — Canadian director James Cameron may be on track to set more records with the home release of "Avatar," if first-day sales are any indication.

Robust sales in the U.S. and Canada had some observers predicting a titanic triumph for the alien adventure's Thursday debut on the high-resolution Blu-ray format, with the Hollywood Reporter noting "Avatar" set a U.S. record for first-day sales at 1.5 million copies.

"The Dark Knight" held the previous Blu-ray record.

An estimated 335,000 DVD and Blu-ray copies of the movie were sold in Canada, said a spokeswoman for Twentieth Century Fox Home Entertainment, adding that she could not confirm if that was a record.

At HMV stores, first-day Blu-ray sales of "Avatar" surpassed the mark set by "The Dark Knight," said director of product Ken Kirkwood.

Overall sales, including DVDs, put "Avatar" "neck and neck" with "The Dark Knight," he added.

But considering "The Dark Knight" had the advantage of being released in December 2008, in the heart of the holiday shopping season, "Avatar" sales were very impressive, Kirkwood said.

At Future Shop stores, "Avatar" sold well but did not exceed the first-day sales of "The Dark Knight," a spokesman said.

"Avatar" hit stores Thursday, on Earth Day, rather than on a Tuesday, the industry standard. That may jeopardize the movie's chances of setting first-week sales records.

Some fans may also hold off buying the movie since the bare-bones release is expected to be trumped by a four-disc box set due in November.

Still, Kirkwood called the early numbers "massive" and said he believes it's the first release HMV has had in which Blu-rays outsold DVDs.

Producer Jon Landau said the "Avatar" box set will feature an additional six minutes of footage plus behind-the-scenes content making it "the best possible Blu-ray release ever." A 3D release is also planned, but no date had yet been set.

"The idea is that this first release is all about the quality of the presentation and preserving the movie the way it was presented in theatres," Landau said in an interview.

"The release later in the year will be an immersive fan experience where they will have added scenes ... added content that wasn't in this version of the movie."