Tributes are seen in Parliament Square following a recent attack in Westminster, London
WASHINGTON (Reuters) - British investigators are having to make basic checks into the background of London attacker Khalid Masood who previously crossed security officials' radar around five years ago, a European government source told Reuters on Friday.
Before he killed four people in Britain's deadliest attack since the 2005 London bombings on Wednesday, Masood was considered by intelligence officers to be a criminal who posed little serious threat.
The source said authorities had "no intelligence about how he got to this point" immediately after the attack and that he had been a "very marginal" figure when his name featured in a previous investigation.
The source, who is familiar with the current investigation into Masood, said that the British counter-terrorism investigation in which his name had previously appeared dated from about five years ago.
The source would not disclose the precise nature of that investigation and said interest in Masood dissipated rapidly.
Because they had so little information on his recent activities, investigators were now having to do very basic inquiries to build up a picture of his recent background and activities, the source said.
(Reporting by Mark Hosenball, writing by Michael Holden and David Milliken, editing by William Schomberg)