First, it was filthy conditions at the athletes' village; then it was concerns about security.

Now, the troubled Commonwealth Games are facing a new crisis, with reports that as many as 15 swimmers on the England and Australia teams have contracted cases of "Delhi belly" that they're blaming on the water at the aquatics centre. 

England's swim team doctor said Thursday that eight to 10 competitors were ill with what appeared to be a stomach virus.

Australia has reported that at least six swimmers are sick, including stars Andrew Lauterstein and Hayden Stoeckel, who pulled out of their events on Thursday.

But the worries didn't slow down Canadian athletes, who won nine gold medals on the day -- boosting their total at the Games to 11 golds.

Canada's Brent Hayden won swimming gold in the men's 100 freestyle. There were also three Canadian women's wrestling champions, two synchronized swimming golds and three more in the throwing events at the track.

A spokesman for Swimming Canada said while Hayden, from Mission, B.C., reported a mild case of "Delhi belly" Wednesday, that didn't stop him from posting the fastest time in the world this year.

Meanwhile, the source of the illnesses was being investigated. Australian chef de mission Steve Mongeghetti said that while at least five team members from sports other than swimming had become ill, he thought the fact that most of those being affected were swimmers suggested the illnesses were likely not food-related.

"We're all eating in the dining hall, we're all eating the same food and there's very few cases across the board. It seems like there's more cases in the one sport," he told the Sydney Morning Herald.

Moneghetti said it was possible the pool or its facilities could be making the swimmers sick, but he said it was too early to be sure.

Among the British team, Commonwealth Games England said that of the 541 England team members in the Village, about eight per cent of the team has had some kind of mild stomach conditions over the past 28 days.

"These levels are lower than we expected coming into this environment. But we are not complacent and continue to reinforce the need to be vigilant in areas like hand hygiene," read a team statement.

"Separately, we have asked for reassurances as to the water quality at the aquatics venue."

England team spokesman Caroline Searle said athletes were being affected by a "mild 24-hour stomach condition." England swim team spokesman Dave Richards said reports of the sickness had been wildly exaggerated. "No swimmer has missed a competition at all," he said.

Commonwealth Games Federation president Mike Fennell told a news conference Thursday that officials will investigate the matter urgently and conduct tests on both the main pool and the warm-up pool at the Dr. S.P. Makherjee Aquatic Complex.

"If there is something unsafe, then you can't swim in that water," Fennell said. "It's a matter we have to deal with, with a great deal of urgency."

With only two days left of swimming events, Fennell was asked if competition might be cancelled or moved if tests showed the pools were unsafe. He replied he didn't want to speculate on that.

"If there is something unsafe, you cannot swim in that water. It is a matter we have to deal with a great deal of urgency," he said.