ANCHORAGE, Alaska (AP) — Four-time champion Jeff King maintains his lead Thursday in the Iditarod Trail Sled Dog Race.

King was the first musher to reach the community of Ruby, Alaska, which is the first checkpoint along the 1,875-mile Yukon River.

There were two other mushers en route to Ruby from the previous checkpoint in Cripple. Brent Sass and Aliy Zirkle breezed through the Cripple checkpoint, chasing King.

Several mushers appeared to be taking their mandatory 24-hour layover in Cripple. Both Sass and Zirkle have taken that layover, but King hasn't done so.

Race officials said one musher, Robert Redington, was inadvertently allowed to leave the checkpoint in Nikolai 50 minutes early at the conclusion of his 24-hour layover. Race director Mark Nordman said in statement that it was not Redington's fault, and the 50 minutes will be added to the mandatory eight-hour layover that all mushers must take along the Yukon River.

Eighty-five mushers began the 1,000-mile race to Nome on Sunday just north of Anchorage. The winner is expected in the Bering Sea coastal town of Nome sometime early next week.