'Steering casualty' preceded New Orleans cruise ship collision, says NTSB37 minutes agoSareen Habeshian
Getty Images A tugboat stabilizes the riverboat American Heritage, which lies on its side partially submerged in water. A green, red and white tanker, seen from the rear, is next to both vessels. Getty Images

The tanker that struck a cruise ship docked in New Orleans on Friday had a "steering casualty", officials said, citing preliminary findings into the collision.

It remains unclear what caused the steering failure on the Atlantic Asphalt cargo vessel, the National Transportation Safety Board (NTSB) said in a media briefing on Sunday.

The collision left 32 people from the stricken American Heritage riverboat in hospital with non-critical injuries, but no-one was unaccounted for.