Switzerland's attorney general has widened a bribery investigation into a former employee of commodities trader Gunvor Group in the Republic of Congo to include the company itself, Gunvor said in a statement on Monday.

Gunvor said the investigation was expanded to "examine possible organizational shortcomings exploited by the ex-employee to perpetrate alleged acts of bribery of foreign officials".

The Swiss attorney general's office said in a statement it has sought assistance from a number of countries and told Gunvor it is under formal investigation.

Gunvor said the investigation would include its Swiss entity, Gunvor SA, as well as the Geneva branch of its Netherlands-registered Gunvor International BV.

The investigation relates to alleged fraud, embezzlement and money laundering in connection with an oil contract in the West African nation, according to Gunvor and the attorney general.

The attorney general began an investigation into alleged money laundering in late 2011 but lacked evidence to identify any individuals.

In late 2012, Gunvor filed a criminal complaint against a former employee for fraud and embezzlement. It said the ex-employee's acts were unknown to the company.

In 2014, Gunvor dismissed a second employee in connection with the matter and reported the individual to Swiss authorities after "learning of a videotape that highlights alleged misconduct by this employee", it said on Monday.

Gunvor said the firm had since increased oversight and compliance rules "in order to prevent unwanted, independent behaviour" and stopped all business in the country.

Gunvor runs three European refineries and holds stakes in upstream ventures, oil infrastructure and mining companies. Historically a Russia-focused oil trader, it shed its Russian assets, added global offices and expanded into coal, liquefied natural gas, biofuels, power and emissions.