Thirteen people have been arrested in raids by police investigating a multi-million pound bank fraud.
The gang is suspected of opening accounts in false names
The inquiry concerns a gang suspected of opening accounts in false names using counterfeit documents.
A bank employee is among the people being held after officers executed search warrants at addresses in west London, Bradford and Slough.
The City of London Police's Economic Crime Department said it is believed in the region of £3m was stolen.
"This investigation has focused on the addresses of a group of organised individuals who have been fraudulently attacking the UK clearing banks," said Det Sgt Martin Peters.
"During this investigation, we have been working closely with all the financial institutions."
Eight men and five women are being questioned. Twelve of the arrests were made in the Ealing, Hayes and Hammersmith areas of London and one in Bradford.
The raids took place early this morning, and involved a large number of officers.
One eyewitness in west London told the BBC News website: "It was very dramatic. We heard the police using a battering ram to gain access to a flat on the floor below us.
"It was very loud and a bit frightening, as the first we realised that police were in the building was when we heard the breaking noise.
"As we left for work there were around 15 officers in our building, some wearing helmets and hoods. They had left the police vehicle in a nearby street and appeared to move in to the flat at high speed.
"As is often the case with a block of flats we had no idea who lived in the flat that was raided. It appeared to be rented."