The Home Office is not confirming or denying whether any British workers have been involved.
But officials say they are investigating reports which suggest at least one Briton was taken when gunmen stormed a compound belonging to a Lebanese construction company in Nigeria.
ITV News reporter Sejal Karia talks from outside the Foreign Office:
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A quiet night ahead of us weather wise, with a mostly dry day tomorrow.
Ireland's overwhelming support for gay marriage is a message to the world, UN secretary general Ban Ki-moon said.
The owner was arrested after two police officers fell ill from the fake cannabis, known as Mr Nice Guy, Israeli media reported.