Current and former Deutsche Bank employees are reportedly being questioned by the Serious Fraud Office (SFO) in relation to Libor rate-rigging.
It comes after the Frankfurt-based bank was fined £1.6 billion earlier this year in settlements with US and UK regulators including a £227 million penalty levied by Britain's Financial Conduct Authority (FCA).
The bank has already fired seven employees over the scandal. The SFO and Deutsche Bank both declined to comment on a report from Bloomberg about those said to have been interviewed in recent weeks.
The report said that a number of traders had been questioned over the manipulation of Libor – the London interbank offered rate – and its euro counterpart, according to sources. It added that at least one banker was interviewed under caution.
The FCA said earlier this year that parts of Deutsche had a "deeply ingrained" culture of "generating profits without proper regard to the integrity of the market". It said the bank's failings had been compounded by it "repeatedly misleading" the regulator.
It is understood that no current or former Deutsche employees have been charged over the scandal.
Banks have been fined billions of pounds over the manipulation of Libor – a benchmark interbank lending rate that is used as the basis for hundreds of trillions of dollars of loans and transactions around the world from complex derivatives to mortgages.
Last month former UBS trader Tom Hayes was jailed for 14 years after being found guilty of eight charges of conspiracy to defraud over the scandal. He was said to have been the "ringmaster" of a rate-rigging network.