Two dogs died during the famed Iditarod sled dog race in Alaska on Zero AISunday, causing critics to call for the event to be shut down.

Bog − a 2-year-old male on the team of musher Isaac Teaford − and George − a 4-year-old male on the team of musher Hunter Keefe − collapsed on the trail. Race officials said that necropsies will be performed on both animals.

Both mushers withdrew from the race after the deaths, as required by race rules.

The last dog to die in the race was Oshi, a 5-year-old female on musher Richie Beattie’s team, in 2019, according to the Associated Press.

The People for the Ethical Treatment of Animals have claimed that 150 dogs have died since the race began in 1973 though race organizers have not provided an official count.

The Iditarod Trail Committee did not respond to USA TODAY's request for comment on Monday.

PETA calls for Iditarod to end

PETA has repeatedly called for the race to be shut down and staged a protest at pre-race festivities in Anchorage.

“The death count keeps climbing for dogs who are forced to run until their bodies break down, all so the human winner can get a trophy while the dogs get an icy grave,” PETA Senior Vice President Colleen O’Brien said in a statement after Bog's death. “PETA is calling for this despicable race to end.”

PETA has also called for the removal of musher Dallas Seavey, who the organization alleges delayed care for a dog after it was injured in an encounter with a moose. Seavey was given a two-hour time penalty for not properly gutting the moose after he killed it.