An inquiry is under way into alleged cartel activity involving commercial vehicle manufacturers, the Office of Fair Trading has said.
The OFT is understood to have visited the UK premises of Mercedes-Benz as part of the probe.
An OFT spokesman said: "The OFT is investigating suspected cartel activity involving commercial vehicle manufacturers in the UK.
"Investigations are being carried out under both the Enterprise Act 2002 and the Competition Act 1998. The investigations are at an early stage.
"The OFT will not be in a position to conclude whether it considers the law has been infringed until it has completed its investigations and assessed the available evidence."
One individual has been arrested and released on bail in connection with the case, the OFT confirmed.
The OFT has requested information from Scania of Sweden and Germany's MAN as part of the broad-ranging investigation into the pricing of trucks, the Financial Times reported.
The newspaper said the action represents a significant move by the OFT, as it is the watchdog's only criminal cartel case - apart from a failed attempt to prosecute British Airways - to feature businesses that are household names.
Companies involved in price-fixing can be fined up to 10% of their annual turnover.
