Greek police started clearing migrants and refugees out of a sprawling tent camp on the sealed northern border with Macedonia where thousands have been stranded for months waiting in vain for passage to Europe. Reuters witnesses saw four to six bus loads of migrants leaving the makeshift camp of Idomeni early Tuesday morning, with about another dozen more lined up. Greek authorities said they planned to move individuals gradually to state-supervised facilities further south. "The evacuation is progressing without any problem," said Giorgos Kyritsis, a government spokesman for the migrant crisis. Railway tracks between Greece and Macedonia have been blocked by migrants for more than a month, forcing trains to switch routes through Bulgaria further to the east. Some wagons loaded with goods have been stranded on the tracks for weeks.