Germany’s financial regulator has demanded documents from Deutsche Bank as part of an investigation into potential manipulation of gold and silver prices. The probe from the German watchdog comes as regulators step up scrutiny of benchmarks after several global banks were punished with heavy fines for manipulation of the Libor interbank lending rate.

BaFin has grilled Deutsche Bank staff during several on-site inspections in the past few months, according to people familiar with the matter, in a sign of how seriously the German regulator is scrutinising the precious metals markets.

Deutsche Bank is one of five banks which take part in the twice-daily “London gold fixing”, and one of three banks which take part in the equivalent process for silver.