Favorite Australia and arch-rival New Zealand were in ruthless form as rugby sevens made its Olympic debut Saturday, Frenchwoman Camille Grassineau grabbing a piece of history by scoring the first try of the tournament. The Wallabies ran unfancied Colombia ragged in their opening match, Charlotte Caslick scoring a hat trick in the 53-0 rout. There were no worries in their second game as they dispatched Fiji by a 36-0 margin. New Zealand look the closest rival to Australia, with Kayla McAlister — sister of Toulouse-based former All Black Luke — and Portia Woodman both outstanding in lop-sided wins over Kenya (52-0) and Spain (31-5). "I've just got to get over that white chalk to get the points on the board. That's my job," said McAlister, who finished the day with four tries. "No team is weak. This is the Olympics: every game's a final and France is our next one which will be tough." The French, Canada and Britain also finished the day's play unbeaten in blistering conditions with temperatures above 30 degrees celsius (84F) at the 15,000-seater Deodoro Stadium, which was at its best half-full. And it was France's Grassineau who was first on the scoreboard, crossing for a try in her team's opening 24-7 victory over Spain. "The main goal was to win but the first try happened to come to me. It was a try for the team and we made a good start," she said. "We'll see, if in 10 years' time, my name is in the books!" Spanish playmaker Patricia Garcia had the honour of kicking off. Initially a sparse crowd of barely 1,000 had entered the Deodoro Stadium, but that quickly changed under the watchful eyes of IOC President Thomas Bach, World Rugby president Bill Beaumont and guest Sachin Tendulkar, the Indian cricket superstar lobbying for his sport's inclusion at the 2024 Games. Brett Gosper, chief executive officer of World Rugby, said the hosting of the tournament was "going to plan" despite swathes of empty seats. "We would have liked a few more people turning up," Gosper admitted, adding that ticket sales were at "around 70 percent on average across the six days" that included the three-day men's competition that starts Tuesday. Turning to Bach, who is also due to attend the men's final, Gosper said: "He's a good friend of rugby, World Cups and other sevens visits that he's made, so he likes his rugby which is great." The tournament signaled the first time since 1924 that rugby has been played at the Olympics and the debut for sevens, the previous four incarnations featuring men's 15-a-side tournaments. On the pitch, Fiji caused the upset of the day, trumping the United States 12-7 with Bach watching, before losing to the Wallabies in the day's final game. Two tries by Luisa Tisolo and Timaima Ravisa either side of one from American Alev Kelter were enough to see the islanders home in a tight match brought to a juddering end with a memorable man-and-ball tackle by Lavenia Tinai on Jessica Javelet.