EDMONTON - The Edmonton Humane Society says it will investigate a complaint by animal welfare groups about the treatment of the lone elephant at the city's Valley Zoo.

The groups -- Zoocheck, People for the Ethical Treatment of Animals and Voice for Animals -- made a formal report to the society Tuesday after losing a court bid earlier this year to have Lucy moved to a U.S. sanctuary.

It's the second time animal rights groups have made a complaint to the humane society about Lucy's health and the latest salvo in their long-running battle to have her moved out of the Edmonton zoo.

Humane society spokeswoman Shawna Randolph said a previous investigation in 2007 determined everything was OK.

The society also does yearly checks on the health of animals at the zoo, she said. Still, an investigator will be assigned to review the new complaint.

"Although this is a high-profile animal, we're not treating this any different than any other case," Randolph said.

"We take all of these requests to look into the welfare of animals very seriously and we're going to in this case."

Julie Woodyer with Zoocheck said the new complaint is much more detailed than the 2007 one. She said the groups have provided the humane society with a half-metre-high stack of expert reports and other documents to support their concerns.

"We're laying out in tremendous detail exactly why we believe Lucy is suffering."

Lucy is a 35-year-old Asian elephant and animals rights groups have long suggested she is lonely and ailing, especially during the harsh Edmonton winters. The average lifespan of an Asian elephant in captivity is 44.8 years, according to the Canadian Association of Zoos and Aquariums.

The city, which owns the facility, has argued Lucy has received the best possible care and a move to an elephant sanctuary in the United States could kill her.

The case has become a magnet for celebrities, including game show host Bob Barker and actor William Shatner, who have urged the Valley Zoo to give up

Woodyer said Tuesday's complaint stems from the court action. In rejecting a relocation bid from the groups, the judge ruled that complaints about animal health must be dealt with through proper channels, meaning a humane society investigation.

Woodyer fears the humane society won't do a thorough job, even though the organization has no affiliation with the city.

"When I filed the first complaint, back in 2007, I was told very clearly that they had a positive relationship with the zoo," she said. "Well, that in and of itself is a problem right from the start, because an organization that is investigating someone shouldn't be having a pre-existing relationship."

Randolph said the 2007 complaint was thoroughly investigated and this one will be too.

She did warn that a review will take some time to complete because the Edmonton Humane Society only has two investigators.

"It's going to take a long, long, long time to investigate, because ... this is one of several files to be investigated."