A port official said he was told the North Sea collision produced "a massive fireball" and the cargo ship's owner said one crew member was missing.

A cargo ship carrying a toxic chemical hit a tanker carrying jet fuel for the U.S. military off England, setting both vessels on fire and sending fuel pouring into the North Sea.

Fears of an environmental disaster eased on Wednesday, two days after a container ship ploughed into a stationary U.S. fuel tanker off northeast England, as the vessel's owner said the detained captain was a Russian national.