Amy Yang rolled in four consecutive birdies in a round of 4-under 66 for a three-stroke lead after two rounds of the women’s US Open.

While the bulk of the field tried to solve the sloping greens at Lancaster Country Club in Pennsylvania, Yang charged into the lead with birdies on 11-13 to place the 25-year-old South Korean at 7-under overall.

Stacy Lewis, last year’s runner-up, and Japan’s Shiho Oyama were tied for second at 4-under.

Marina Alex, part of a three-way tie for the lead after one round, carded a 1-over 71 and was next at 3-under.

Australian Karrie Webb, also first round co-leader, had a 2-over 72 and was in a large group at 2-under.

That group includes top-ranked and two-time champion Inbee Park (70), first-round co-leader Jane Park (72) and Michelle Pressel (70).

Defending champion Michelle Wie rebounded from an opening 72 with a 2-under 68 and was seven shots off the lead.