KOH TAO, Thailand — Promoters call the Thai island of Koh Tao a paradise. Dive resorts boast of its crystal-clear waters, and Western tourists flock to its lively beach bars.

But among some foreigners, Koh Tao has taken on a more sinister reputation. At least nine European tourists have died or disappeared there since 2014. British tabloids began calling it Death Island.

Now, the claim of a 19-year-old British tourist that she was raped on Koh Tao in June has again focused attention on the island’s troubled history and called into question police handling of serious crimes against tourists.

Initially, the police denied that a rape occurred and arrested a dozen people for posting about it on Facebook. The police also issued arrest warrants for an online newspaper editor in Britain and a Facebook page administrator in California.