GLASGOW -- It was only a matter of time before a doping scandal hit the Commonwealth Games. This time, it involved a 16-year-old female weightlifting gold medallist from Nigeria.

Chika Amalaha tested positive for the diuretic amiloride and masking agent hydrochlorothiazide -- both banned by the World Anti-Doping Agency -- after winning the 53-kilogram weight class last Friday, games officials said Tuesday.

She's the first athlete to test positive during the games, which opened last Wednesday night.

Amalaha asked for the backup "B" sample to be tested, which will happen in London on Wednesday. If that sample also comes back positive, she will be stripped of her medal.

"It shows we have a very robust anti-doping program in place," Commonwealth Games Federation chief executive Mike Hooper said. "It sends a strong message to anybody in any sport that if you go down the path of doping, any substance to enhance performance, they will be caught ... it's an ongoing battle."

It's the second Commonwealth Games in a row that Nigeria has been in the doping spotlight. Four years ago in New Delhi, three of the four doping cases involved Nigerian runners, including women's 100-meter gold medallist Osayomi Oludamola.

Elsewhere at the games on Tuesday:

CANADIANS, KIWIS 1-2: Catharine Pendrel of Canada, the 2011 mountain bike cross-country world champion who finished ninth at the 2012 London Olympics, won gold in the women's cross-country race at the Cathkin Braes Country Park course in Glasgow. Her Canadian teammate Emily Batty took the silver, with Rebecca Anderson of Australia earning the bronze. "We trained well as a team," Pendrel said. "I knew from training and the nationals that Emily was on fire, so I'm proud she got silver." In the men's race, New Zealanders were 1-2, with Anton Cooper beating Samuel Gaze by just three seconds for gold. Australian Daniel McDonnell took the bronze.

A ROYAL RETURN: Prince William, the Duke of Cambridge, and his brother, Prince Harry, played football at a coaching project in Glasgow while William's wife, the former Kate Middleton, attended a charity reception Tuesday as the royals were in the Commonwealth Games city for the second day in a row. William and Harry played in a five-a-side game with other coaching prospects and then joined in for a photo. The coaching project was launched by the brothers and Kate two years ago. William and Kate also attended the athletics competition on Tuesday.

SHOOTING FOR GOLD: Australian shooters won both golds on offer in early events, with English and Indian competitors taking the minor medals. Adam Vella defeated Aaron Heading of England in the men's trap final, and Manavjit Sandhu of India took the bronze. David Chapman of Australia took gold in the 25-meter rapid-fire pistol, India's Harpreet Singh took silver and Kristian Callaghan of England earned the bronze.

POOLEY RETIRES: 2008 Olympic silver medallist Emma Pooley announced she will retire from cycling after she competes for England in Sunday's road race. Pooley won a time-trial silver medal in Beijing and a world title in the same discipline in 2010.