Fraudsters spoofed bank phone numbers to extract account details.
Nine people have been arrested by police investigating a £60m fraud case targeting business banking customers.
Seven men and two women were arrested on suspicion of conspiracy to defraud and money laundering.
The Met said victims had their phone numbers masked in order to make it appear as though they were getting a legitimate call from their bank.
The fake numbers were then used to glean account details.
Money was then transferred into accounts under the suspects’ control and withdrawn from ATMs across the UK, the Met said.
Police recovered a “significant amount of cash” through raids on 14 addresses in Ilford, Watford, Slough and Scotland.
Dongles, SIM cards, mobile phones and laptops were also seized.
The arrests followed a collaboration between the Met Police Service’s Cyber Crime and Fraud Team and a number of other police forces including Police Scotland, West Yorkshire Police and Greater Manchester Police.
All the suspects arrested are currently in police custody.