LONDON British security firm G4S (GFS.L) said on Monday the Serious Fraud Office (SFO) had opened an investigation into its criminal electronic tagging contract.
In July the British government placed all contracts held by G4S and its rival Serco (SRP.L) under review after an audit showed they charged for tagging criminals who were either dead, in prison or never tagged in the first place.
The government had then asked the SFO to consider carrying out an investigation into G4S and has since also referred Serco to them.
G4S said on Monday it would co-operate fully with the SFO investigation. Shares in the firm were down 1.2 percent to 251.2 pence at 1108 GMT.