A tornado landed at the stadium where thousands of people were expected to gather for the inauguration of the Central American and Caribbean Games on Saturday, injuring at least five people and forcing officials to delay the opening ceremony.
The storm ripped down scaffolding workers were using to add final touches to the Jose Figueroa Olympic Stadium, toppling the metal onto cars below.
"At the moment we have information that people are injured and the meteorologists have told us they expect two similar episodes during the afternoon," police Col. Francisco Carbo told The Associated Press.
One of the victims had three of his fingers amputated and a 3-year-old received minor injuries on one hand.
Officials evacuated people who had already arrived at the stadium, which is close to the shore on Puerto Rico's western coast, and scrambled to secure lighting towers and tents ahead of further winds.
Competition in the games is scheduled to start today and run through August. 2. Thirty-one countries will participate including diving, swimming, track and field, fencing and boxing.