With their mandatory 24-hour layovers out of the way, two challengers led defending champion Susan Butcher in a virtual neck-and-neck dash Thursday for the midway point in the Iditarod Trail Sled Dog Race.

DeeDee Jonrowe and Tim Osmar left Ophir one minute apart early Thursday, the sixth day of the 1,163-mile, Anchorage-to-Nome trek.Butcher, one of only two mushers to win the Iditarod four times, left Ophir 40 minutes later.

Ophir, a former mining town, is 476 miles into the race. The next checkpoint is the ghost town of Iditarod, 90 miles away and the official halfway point.

Terry Adkins was the first into Ophir, arriving early Wednesday. But he chose to take his 24-hour layover there, while others took their break earlier.

Snow and high winds threatened to slow down what so far has been a fast Iditarod.

An inch and a half of wet snow fell early Wednesday in McGrath, followed by winds that whipped the snow into drifts. The forecast for the Lower Yukon Valley, where mushers were heading, was for 2 to 4 inches of snow.

Some mushers had said they were tiring of the fast trail, which had been hardened by freezing rain.

"The dogs, they got to rest. You can't go to Nome without resting them," said Lavon Barve.

Butcher set a course record in 1990 by finishing in 11 days, 1 hour and 53 minutes.