JUNEAU (AP) — Veteran musher Lance Mackey has had his 21st place finish in this year's Iditarod Trail Sled Dog Race vacated because of a failed drug test, race officials announced Thursday.

Mackey is a four-time Iditarod winner and a cancer survivor who had acknowledged using marijuana on the trail before the race began testing mushers in 2010.

Thursday's statement said a urine sample taken at a checkpoint during this year's race tested positive for methamphetamine.

In addition to being disqualified, the race said Mackey will have to return $1,049 in prize money for this year's race, which was held in March.

The statement quotes Mackey as saying he is in the process of making arrangements to go to a treatment center, "where I can get the professional help and real change I need. I'm ready to confront this with all of my focus and determination."

The Associated Press left a message seeking comment via Mackey's kennel Facebook page.

"While this is a very unfortunate event, we hope this disqualification will be a turning point in spurring Lance on the trail to recovery," Iditarod Board President Mike Mills said in the statement, calling Mackey "one of our Iditarod heroes who is going through a tough time in his life."

Iditarod CEO Rob Urbach called Mackey a "truly great dog man." He said the primary concern is that Mackey finds "the support and treatment he needs to get healthy and hopefully finish his most important race."

Mackey won the Iditarod from 2007 through 2010, the year the race began drug testing of mushers.

Mackey in 2010 said he believed the change was directed at him but he also said he was abiding by the rule.