Possible rare assault on a merchant ship in the Gulf ...

WaPo/ here

"... Authorities on both sides of the narrow Strait of Hormuz dismissed suggestions of a deliberate strike, however, pointing instead to natural causes. The U.S. naval fleet that patrols the region said the cause of the blast remains unclear. If the tanker was attacked, it would be a rare assault on a merchant ship in the Gulf or at the Strait of Hormuz, a transit point for about 40 percent of oil shipped by tankers worldwide.

Al-Qaida has in the past carried out attacks on oil infrastructure on land ..."