LESBOS, Greece (Reuters) - Thousands of migrants were left without shelter on Wednesday after overnight fires gutted their overcrowded camp on the Greek island of Lesbos, and authorities warned that some asylum seekers who tested positive for COVID-19 could spread the virus. The Moria camp, which hosts more than 12,000 people, was "probably totally destroyed", a Greek migration official said. Authorities said they were investigating arson at the sprawling camp. Early Wednesday evening, a new fire broke out, sending those who remained on site fleeing.