SINGAPORE (AP) — Worsening smog in Singapore prompted swimming World Cup organizers to cancel 15 finals races just an hour before the session was to start.

Singapore has been shrouded with smoke and haze from Indonesian forest fires for weeks.

Organizers from FINA, the International Swimming Federation, scrapped the races as the Pollutant Standards Index, or PSI, the country's main measure of air pollution, climbed toward 200.

Spectators will be given a refund for tickets, but will miss the closely-watched women's 200-meter backstroke showdown between Australia's world champion Emily Seebohm, U.S. multiple Olympic champion Missy Franklin, and Hungary's world 200-meter individual medley record holder Katinka Hosszu.

Racers were awarded medals based on their heats times. Franklin, who qualified fastest with a time of 2 minutes 4.06 seconds, won the gold, while Seebohm took silver with a time of 2:05.81. Hosszu settled for bronze with a time of 2:06.81.

Other cancelled races included the men's 200-meter butterfly and women's 50-meter freestyle.

After organizers released a statement and cancelled the evening session, noting the "upward trend" of the PSI readings, it hit the day's high of 242.

The morning session of heats was held as planned, and two more sessions Sunday were scheduled to go ahead.

In the Singapore leg of the event, four sessions were to run over two days this weekend. The event had earlier run in cities such as Moscow, Hong Kong and Beijing. The next leg is to be held in Tokyo on Oct. 28 and 29.

At a meeting held in Jakarta on Oct. 1, Indonesian officials turned down Singapore's repeated offers to help with fire-fighting operations, saying they could handle it on their own, although earlier Vice President Jusuf Kalla had said the country was open to help from all countries including Singapore.