Charley Hull remains well placed to challenge for Olympic gold after moving within two strokes of midway leader Inbee Park in Rio.
The Brit followed Wednesday’s opening-round 68 with a five-under 66 to sit alongside Brooks Henderson in a tie-for-third, as Park fired a second successive 66 to move in to top spot.
A round-of-the-week 63 from Stacy Lewis sees her sit one off the pace in second, while world No 1 Lydia Ko is in the group with Irish amateur Leona Maguire seven shots back.
Resuming three strokes off the pace, Hull rolled in a 15-footer for birdie at the first but missed the next green on her way to a bogey-five.
Successive gains from the sixth saw Hull reach the turn in 33, before the Englishwoman shot up the leaderboard by birdieing her final three holes.
Park mixed six birdies with a solitary blemish on her way to setting the pace, while Lewis recovered from a three-putt double-bogey at the 14th to finish with four successive gains.
“I don’t know if something seemed to click and I got some more confidence as the day went on,” Lewis said after a round containing 11 birdies. “Any time you see some putts go in, it frees up the swing a little bit more. But I didn’t expect this at all.”
First round leader Ariya Jutanugarn stuttered to a level-par 71 to slip four shots off the pace, with Britain’s Catriona Matthew a further stroke behind after a much-improved 66.
On a day of low scoring, Ireland’s Leona Maguire rebounded from an opening 74 with a superb 65, while team-mate Stephanie Meadow recorded a 66 following a disappointing 77 on Wednesday.
“Tee to green I played really well again but holed some more putts today which was key,” said Maguire, who carded five birdies in six holes from the ninth.
“I spent a while on the putting green on Wednesday and had a chat with Paul [McGinley, Irish team captain], but I didn’t try and dwell on it too much, I just tried to come out this morning all guns blazing and shoot a low one.”