An autopsy failed to determine what caused the death of a 32-year-old Argentine athlete during the swimming leg of the New York City Triathlon on Sunday.

The city medical examiner's office said Monday more tests are needed for Esteban Neira, who died Sunday morning during the 1,500-meter swim. Swimming is the first leg of an event that includes a 40-kilometer bike ride and 10-kilometer run.

The medical examiner's office said it needs to conduct tissue and toxicology tests. A final report should come in two weeks.

Several of the 3,000 competitors swimming in the Hudson River complained of jellyfish stings, which can cause allergic reactions and in rare cases can be fatal.

(Copyright 2008 by The Associated Press. All Rights Reserved.)

AP-NY-07-21-08 1726EDT

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