A massive fire broke out Friday at a sprawling tire dump in a town near Madrid, sending a spectacular cloud of thick black smoke into the air that was visible for at least 30 kilometers (20 miles). Ten teams of firefighters were sent to try to put out the blaze in Sesena, but it was still raging more than 10 hours after it started. Authorities suspect someone intentionally started the fire before dawn at the tire dump, thought to be Europe's largest, Sesena Mayor Carlos Velazquez said in an interview on Cadena Ser radio. Residents in several parts of Sesena were ordered to stay indoors and shut their windows, he said. Police said classes at one school were canceled and authorities urged drivers traveling nearby to keep their windows closed. Two major highways pass close to Sesena. Spain's leading El Pais newspaper reported that the dump holds 100,000 metric tons (110,000 tons) of used vehicle tires.