Caroline Hedwall, despite a double bogey and a bogey, is alone in fifth one stroke off the lead. Seven players, including defending champion Suzann Pettersen, Jiyai Shin and Michelle Wie, are tied at 3-under 69. World No. 1-ranked Inbee Park is in a group of five at 2-under.
Hull-Kirk, starting at No. 11, had five birdies in the first five holes and played the front nine even with two birdies and two bogeys.
Nordqvist scattered six birdies and one bogey across her card. Pak rebounded from a third-hole bogey with three birdies in the next four holes. She had three more in the first five holes of the back nine.
Yang had a 5 on the par-4 second hole before her birdie string started two holes later. She added a birdie at 11 for her 67.