Thickening haze in Singapore prompts cancellation of World Cup swim races

The financial skyline is seen through a thick haze, Saturday, Oct. 3, 2015, in Singapore. The haze is caused by the burning of forests in Indonesia's Sumatra and Borneo islands. (AP Photo/Wong Maye-E) (The Associated Press)

A man wears a face mask on a public bus, Saturday, Oct. 3, 2015, in Singapore. The haze is caused by the burning of forests in Indonesia's Sumatra and Borneo islands. (AP Photo/Wong Maye-E) (The Associated Press)

People wear face masks to protect themselves from the haze, as they cross the street at a local mall, Saturday, Oct. 3, 2015, in Singapore. The haze is caused by the burning of forests in Indonesia's Sumatra and Borneo islands. (AP Photo/Wong Maye-E) (The Associated Press)

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 — which included a closely-watched women's 200-meter backstroke final — as the Pollutant Standards Index, or PSI, the country's main measure of air pollution, climbed toward 200.

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