Yesterday at about 10:30 in the morning, a half-kilometer long oil slick was seen on the Smichov side of the Vltava near the railway bridge. Firemen from the Holesovice and Central stations joined the chemical brigade from Petrin to clean up the environmental contamination. The primary information pointed the blame on a botel said Katerina Suchanska, spokeswomen for the Prague Firefighters.