Alexander Dale Oen of Norway swims during his semifinal heat of the Men's 100m Breaststroke on Day Nine of the 14th FINA World Championships at the Oriental Sports Center on July 24, 2011, in Shanghai, China. He won the event the next day. (Adam Pretty/GETTY IMAGES)

Alexander Dale Oen, a world champion swimmer who was one of Norway’s top medal hopes for the London Olympics, died of cardiac arrest April 30 after collapsing in his bathroom at a training camp in Flagstaff, Ariz. He was 26.

The president of the Norwegian swimming federation, Per Rune Eknes, confirmed the death to the Associated Press. He said it was unclear what led to the cardiac arrest.

In a statement, the federation said the 100-meter breaststroke world champion was found collapsed on the floor of his bathroom and was pronounced dead at a Flagstaff hospital.

Mr. Dale Oen earned his biggest triumph in the pool at last year’s world championships in Shanghai when he won the 100-meter breaststroke, a victory that provided some much-needed joy in Norway just three days after the massacre by right-wing extremist Anders Breivik that killed 77 people — including children at a summer camp.

Mr. Dale Oen dedicated the win to the victims of that massacre, pointing to the Norwegian flag on his swim cap after the finish to send a message back home.

The Norwegian team is holding its camp in Flagstaff ahead of the Olympics. The federation said Mr. Dale Oen had only had a light training session and had played golf that day. But teammates became worried when the swimmer spent an unusually long time in the shower and entered his bathroom when he failed to respond to their knocks on the door.

Alexander Dale Oen was born in Bergen, Norway’s second largest city, on May 21, 1985. He started swimming at 4 and said on his Web site that the sport “came very easy and natural for me.”

He is the second high-profile athlete to die of cardiac arrest recently, after Italian soccer player Piermario Morosini collapsed on the field during a Serie B game for Livorno last month. That came just a month after Bolton midfielder Fabrice Muamba collapsed in a soccer game in London but survived.

— Associated Press