A tanker traveling through the San Francisco Bay is leaking fuel - and authorities don't know why.

An oil tanker, the Dubai Star, is currently being checked after authorities found a mile-long sheen of leaked bunker fuel trailing behind the ship in the bay south of the Bay Bridge.

The Coast guard is currently investigating the fuel leak to determine the cause - and the exact origin. According to officials, the Dubai Star has not been in any collision of any kind.

According to officials, the leak began during a transfer of fuel.