EDMONTON, Canada Greek Olympic champion Konstadinos Kederis emerged from the pack with a startling burst to win the men's 200 meters on the seventh day of the world championships on Thursday.

Kederis, the first Greek man to win an Olympic track medal since the 1896 Athens Games, shot through the line in 20.04 seconds, two strides ahead of the field.

A photo finish was needed to separate the other seven runners with Jamaican Christopher Williams getting the silver and American Shawn Crawford and Kim Collins of St. Kitts sharing the bronze.

Kederis shocked opponents and spectators alike when he employed similar tactics to win the gold in Sydney. A converted 400 meters runner, he did not take up the 200 until the start of last year.

The fates have been on his side since.

Last year both defending Olympic champion Michael Johnson and world champion Maurice Greene failed to finish the U.S. trials final and were accordingly left out of the U.S. team.

This year Greene and 1997 world 200 champion Ato Boldon of Trinidad withdrew after the 100 meters final through injury, Reuters reported.

"It is not my problem whether Ato boldon or Maurice Greene are running against me," shrugged Kederis. "It's theirs."

Before competition started on Thursday evening the International Association of Athletics Federations (IAAF) announced the first positive test in track and field for the blood-boosting drug epo (erythropoetin).

IAAF Secretary General Istvan Gyulai told a news conference an unidentified athlete had tested positive but confirmed it was not Russian world indoor 3,000 meters champion Olga Yegorova.