Norway's Suzann Pettersen shrugged off the loss of her yardage book to surge into a share of the lead with South Korean Lee Mi-hyang after the first round at the Manulife LPGA Classic in Cambridge, Ontario on Thursday.
Pettersen, the 2015 champion at Whistle Bear Golf Club, plundered six birdies on the front nine en route to an eight-under-par 64 on a day when 65 players broke par in ideal conditions.
World number two Ariya Jutanugarn, of Thailand, made a smooth start with a 67, while Germany's defending champion Caroline Masson carded 70.
Co-leader Pettersen was delighted with her score, especially after a less-than-ideal preparation.
“I lost my yardage book before getting here,” she told reporters. “I had to get all my new notes, which is kind of a big deal because I have a lot of good notes from the past. Had to start from scratch.
“We woke up this morning to perfect conditions. You can fire at pins and get to par-fives, which is fun.
“Solid eight-under so no complaints. On a course like this you should score low but it’s got to match your game. You’ve got to make putts."
Lee, meanwhile, made a fast start with an eagle at the par-five third on her way to a tie for the lead.
“I played good at the par-fives, that's why I can hit the eight-under today,” said the winner of one LPGA event, who is currently ranked 61st in the world.
(Reporting by Andrew Both in Cary, North Carolina, editing by Nick Mulvenney)