The slender Mexican shot a flawless seven-birdie, 7-under 65 that will give her a one shot edge over South Korea's Sun-Ju Ahn, Brazils' Angela Park and Taiwan's Candie Kung heading into Friday's second round.

The 26-year-old Ochoa has not played a tournament since the end of June, but her hunger was clear as she reduced the back nine to 30 shots.

On a day of sweltering heat, Ochoa ran cold over the front nine, but rebooted her mechanism at the turn and coming home was red hot with half a dozen birdies.

A six-time winner already this season, the Mexican could not have been happier.

"I rolled in putts on the 10th and 11th and it got my confidence going," said the 26-year-old, who defends the Ricoh Women's British Open at Sunningdale next week.

"I'm glad to be at the top and I'm really happy with my position. But I still have to be patient, there are another three rounds to go.

"It's good to be back after the break. I needed to recharge the batteries and now I want to win my first Evian Masters."

A slightly frustrated Annika Sorenstam, the champion in 2000 and 2002 who like Davies posted an opening 71 , was relieved that it was only the first round.

"I wish I'd scored a little better, but there are still a lot of holes to go," said the 37-year-old, who has already announced she will retire at the end of the year.

"But I know this course very well and so I hope I can capitalise on it over the next three days."

The Swede managed four birdies, but her card was ruined by three bogeys - including three-putts at the sixth and 15th.

England's Karen Stupples, who has been the best of the British players on the LPGA Tour in America this year, pulled out before the start due to illness.

ALL THE FIRST ROUND SCORES
(USA & Kor unless stated, par 72):

65 Lorena Ochoa (Mex)

66 Sun Ju Ahn, Angela Park, Candie Kung (Tai)

67 Juli Inkster, Meena Lee, Angela Stanford, Laura Diaz, Suzann Pettersen (Nor)

68 Young Kim, In Kyung Kim, Amy Yang

69 Linda Wessberg (Swe), Natalie Gulbis, Shi Hyun Ahn, Morgan Pressel, In-Bee Park, Song-Hee Kim, Hwa seon Lee

70 Cristie Kerr, Paula Creamer, Ji-Young Oh, Ya-Ni Tseng, Se Ri Pak, Momoko Ueda (Jpn), Meaghan Francella, Catrin Nilsmark (Swe), Trish Johnson, Hee Young Park

71 Laura Davies (Eng), Giulia Sergas (Ita), Annika Sorenstam (Swe), Eun Hee Ji, Jin Joo Hong, Sarah Lee, Teresa Lu (Tai), Jimin Kang, Mi-Hyun Kim, Na Yeon Choi, Sophie Giquel (Fra)

72 Lindsey Wright (Aus), Karrie Webb (Aus), Hee-Won Han, Becky Brewerton (Gbr), Helen Alfredsson (Swe), Julieta Granada (Par), Christina Kim, Rebecca Hudson (Eng), Ji-Yai Shin, Emma Zackrisson (Swe), Sherri Steinhauer, Mhairi McKay (Sco), Katherine Hull (Aus)

73 Carin Koch (Swe), Diana D'Alessio, Sophie Gustafson (Swe), Maria Hjorth (Swe), Brittany Lang, Hye Jung Choi

74 Minea Blomqvist (Fin), Sun Young Yoo, Jane Park, Pat Hurst, Karine Icher (Fra), Gwladys Nocera (Fra), Jee Young Lee, Ai Miyazato (Jpn), Nicole Castrale, Jeong Jang

75 Paula Marti (Spa), Rachel Hetherington (Aus), Catriona Matthew (Sco), Martina Eberl (Ger), Bo-Bae Song

76 Joanne Mills (Aus), Nikki Garrett (Aus)

77 Wendy Doolan (Aus), Ashleigh Simon (Rsa), Na On Min (Jpn), Silvia Cavalleri (Ita), Brittany Lincicome, Reilley Rankin

78 Lotta Maria Wahlin (Swe), Anna-Lise Caudal (Fra)

79 Louise Friberg (Swe)

80 Tao-li Yang (Chn), Bettina Hauert (Ger), Lisa Hall (Eng), Leta Lindley