The Seine has been clean enough for swimming for most of the past 12 days, Paris City Hall claimed Friday, just weeks before the Olympic Games.

"The water quality met the required standard for 10 or 11 of the past 12 days," City Hall official Pierre Rabadan told broadcaster RFI.

Weather permitting, the river will be the star of the opening ceremony on July 26 and will host the triathlon and swimming marathon events.

The Paris region has experienced unseasonably heavy rain in recent weeks, raising the Seine's pollution levels as untreated sewage flows into the river.

"We hope the weather will get a little better, but we are not worried about the possibility of holding the competitions," Rabadan said. "They will take place."

He added, however, that there may have to be "modifications," without giving details.

Weather in Paris is forecast to be mostly dry over the final 14 days before the start of the Games.

On July 4, City Hall had already reported that E. coli bacteria levels at the Olympics swimming spot in central Paris had fallen to within acceptable limits for four days.

But the previous week, levels of E. coli – a bacteria indicating the presence of fecal matter – had been above the upper limits used by sports federations every day at the Alexandre III bridge location in central Paris, which is set to be the jumping-off point for the swimming.

At one point, E. coli levels were 10 times the upper limit of 1,000 colony-forming units per 100 milliliters (cfu/ml), with heavy rain over the previous two months leading to fears for the Olympic events.

The Seine is set to be used for the swimming leg of the triathlon on July 30-31 and Aug. 5, as well as the open-water swimming on Aug. 8-9.

French authorities have spent 1.4 billion euros ($1.5 billion) in the last decade trying to clean up the river by improving the Paris sewage system, as well as building new water treatment and storage facilities.