According to the Daily Star, citing friends of the West Virginia-born coal tycoon, the philanthropist's daughter was among those who died.
According to Forbes magazine, Cline started working in coal mines at the age of 15, dropping out of university at age 22 to enter the coal industry.
Cline bet big in the early 2000s, buying up high-sulfur coal reserves in Illinois in the belief that new tech would make the dirty fuel cleaner to burn. He took coal mining firm Foresight Energy public in 2014, and sold his controlling stake in 2015 for $1.4 billion cash. In early 2017 he opened a new mine in Nova Scotia and had another planned in western Canada, according to Forbes.
According to media reports, Cline's mansion in Beckley, West Virginia, featured a lake, a go-kart track, as well as land for horses, goats and llamas. The Daily Star said that Cline was known for his extravagant lifestyle, with a 205-foot luxury power yacht named Mine Games complete with five bedrooms and its own submarine.
Cline was considered responsible for attempting to revive the coal industry in Illinois. Bloomberg previously dubbed Cline the "New King Coal".