- BBC -
The father of a Nigerian charged with trying to blow up a US jet on Christmas Day had voiced concerns to US officials about his son, it has emerged.
An Obama administration official told the New York Times the report had been received, but had been non-specific.
Airports worldwide have beefed up security after the alleged attack.
Mr Abdulmutallab was formally charged by a US federal judge at a Michigan hospital where he is being treated for burns after allegedly trying to detonate a device.
'Sewn in underpants'
The detainee reportedly smiled as agents brought him in to the room in a wheelchair, dressed in a green hospital robe and with a blanket over his lap.
High explosives are believed to have been moulded to his body and sewn in to his underpants.
He was immediately overpowered by passengers and crew aboard Northwest Airlines Flight 253, minutes before it was due to land in Detroit from the Dutch capital Amsterdam.
The suspect was charged with placing a destructive device on the Airbus 330, which was carrying 289 passengers and crew, and attempting to destroy it.
His father, Alhaji Umaru Mutallab, is a prominent banker well-connected in Nigeria's political world, the BBC's Caroline Duffield reports from Lagos.
In recent months the family had become gravely concerned about their son, a former engineering student at University College London.
His political views alarmed his family and his father especially, and Mr Mutallab had approached the US embassy in Abuja, reportedly in November, as well as Nigerian security officials, to voice concerns about his son.
How the accused, who had a valid US travel visa, boarded a flight in Lagos to Amsterdam, despite being on a database listing individuals of concern to the authorities, is now a key question, our correspondent says.
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