IOC inspectors have begun a three-day visit to Rio de Janeiro to check on preparations for the Olympics, which are just 18 months away.

The IOC's coordination commission is visiting venues and meeting with local organizers as Rio races to be ready on time for South America's first games.

Construction work has speeded up in the past year after a top Olympic official described preparations as the "worst" in recent memory.

Concerns remain over water pollution at several venues, the completion of a subway line and delays in building the velodrome and international broadcaster center.

International Olympic Committee President Thomas Bach is also in Rio and will chair a meeting of his executive board later in the week.

Brazil is spending about $14 billion on the Olympics.