Blobs of black fuel oil washed up on the beaches of southwestern France yesterday, suggesting that oil from the sunken tanker Prestige could have reached French shores. Patches of oil dotted several kilometers of beach in the picturesque Landes region near Bordeaux but maritime officials said it was too early to determine whether they came from the Prestige which sank off the Spanish coast in November. These oil patches, found along 35 km of beach, will be analyzed in a laboratory at Brest to determine their origin, a spokesman for the local maritime authorities said. The results of the tests should be available today. The long, sandy beaches of the Landes region, shaded by vast pine forests and dotted with campsites, are immensely popular with surfers and vacationers, and the area lives off tourism. The Prestige, laden with 77'000 tons of fuel oil, sprang a leak on Nov. 13, then snapped in two and sank six days later, unleashing a tide of foulsmelling sludge on Spain's richest fishing grounds and the northwest coast of Galicia. High winds have been driving a massive oil slick from the wreck toward French waters for several days. Spanish media estimate that a cluster of oil slicks now threatening France covers an area the size of New York City. Tuesday plane monitors spotted around 100 small slicks of about 32 feet in diameter some 205 miles from the French coast and heading east into French waters. Our threeday forecasts show this drifting will continue, with strong easterly winds, the maritime spokesman said. Fuel oil has been continually washing ashore on Spanish beaches even though cleanup vessels are clearing the sea's surface.