Lifeboats involved in the search for the crew of an overturned cargo vessel have been stood down for the night.
The search for the eight people who were on board the Cemfjord ship which capsized off the north coast of Scotland will be limited overnight to vessels travelling through the area.
The tug Herakles will stay on scene illuminating the area and warning shipping.
A passing ferry alerted Shetland Coastguard at around 2.30pm today after seeing the ship's upturned hull in the Pentland Firth.
The Wick, Thurso, Longhope and Stromness RNLI lifeboats, the Coastguard rescue helicopter from Shetland, an RAF rescue helicopter and other vessels in the area were involved in the search.
Bill Farquhar, from RNLI Thurso, told BBC News that the NorthLink ferry Hrossey had spotted the hull of the vessel around 10 miles east of the Pentland Skerries, about 15 miles from Wick.
He said the last known position of the ship had been at 1.15 pm yesterday, adding: "The weather at that time yesterday was pretty bad.
"I don't know what has happened after that. There was no mayday as such.
"It is very, very strange, especially with all the weather technology we have nowadays."
Mr Farquhar said: "Whatever happened, it happened very rapidly."
The 83-metre bulk cement carrier had been bound for Runcorn, Cheshire, on the west coast of the UK.
A spokeswoman for the RNLI said the lifeboats had been stood down and are returning to their stations.
It is expected they will resume the search at first light if requested by the Coastguard.
None of the crew have so far been found.