U.S. Coast Guard says 18,300-acre Santa Rosa Island Fire was possibly started by flares from stranded boater

The nearly 18,300-acre brush fire burning on Santa Rosa Island off the coast of Southern California may have been ignited by flares from a stranded boater, according to the U.S. Coast Guard. 

Since starting on Friday, May 15, at around 4:20 p.m., the Santa Rosa Island Fire has burned nearly 18,500 acres of vegetation in the Channel Islands National Park, which is located off the coast of Santa Barbara. The massive fire has burned what appears to be nearly a third of the southern part of the island and remains 87% contained as of Saturday evening. 

Though the exact cause of the blaze remains under investigation, the U.S. Coast Guard on Tuesday said that the blaze was possibly started by a 67-year-old mariner whose sailboat had crashed into the rocks on Friday. They said that he had set off flares to try to signal SOS. USCG's Air Station Ventura shared a photo of the man with the SOS sign that he had made on the island, surrounded by what looked to be charred vegetation. 

The man was rescued and uninjured in the incident, Coast Guard officials said. 

Since igniting, the fire has also destroyed at least two historic structures on the island, which is one of five islands located as part of the Channel Islands National Park. Firefighters say that the South Point Lighthouse is still standing despite being surrounded by flames at one point.

The area, which has been isolated for thousands of years, has allowed for unique plants, animals and archaeological resources to thrie, according to National Parks Service officials. As many as six plant species are specifically found on Santa Rosa Island and nowhere else in the world.