American Nelly Korda shot the day's low of 62 to take sole possession of the lead Thursday after two days of the women's Olympic golf tournament, with Japan's Mone Inami six shots off the pace.
Despite a double-bogey finish, the reigning Women's PGA Championship winner and world No. 1 drove the green to snag an eagle two on the par-four sixth, adding that to nine birdies that built her a four-shot lead and a two-day total of 13-under at the par-71 Kasumigaseki Country Club course.
Korda's closest pursuers are India's Aditi Ashok and two Danish players, Nanna Koerstz Madsen and Emily Kristine Pedersen, who are tied for second. Sweden's Madelene Sagstrom is alone in fifth a further shot back at 8-under.
Inami and Ko Jin Young of South Korea finished in a two-way tie for sixth. The 22-year-old Japanese, who is making her Olympic debut, also eagled the sixth and carded five birdies and a bogey in a 65.
"It was great that I made an eagle. That went well. I used a wedge (to hole out from the edge of the green) and it went as planned. I hope to continue improving my score so I can move up," Inami said.
Nasa Hataoka, the other Japanese competitor also taking part in her first Olympics, followed up on her opening-round 70 with a 68 to move up five places into a share of 11th place. She fired four birdies against a lone bogey that came when she missed a par put from the fringe of the green on the par-5 fifth.
"It's too bad because I had so many chances but I couldn't convert them and lower my scores. My only bogey on the par-5 hole was a waste. I have a wide gap to the leaders. I have to try and catch up," Hataoka said.
U.S. Women's Open winner Yuka Saso, who is representing the Philippines, turned in a 68 in round two to move up 13 spots into a tie for 34th at even-par.
All three medal winners from the Rio de Janeiro Games -- South Korea's Park In Bee, New Zealand's Lydia Ko and China's Feng Shanshan -- are in the field of 60 players which contains all the current top-10 in the world rankings.
Organizers are mulling the possibility of reducing the tournament to 54 holes due to extreme heat and a tropical storm that is in the forecast.
Already a number of caddies, including those for Saso and American Lexi Thompson, were forced to abandon their involvement due to the heat which reached the mid-30s C on Thursday.
