(Sharecast News) - The Financial Reporting Council has launched an investigation into Grant Thornton's audit of outsourcer Interserve's financial statements.The accounting regulator said on Thursday that the investigation will span the years ended 31 December 2015, 2016 and 2017.Interserve announced last month that it was going into administration after plans for a rescue fundraising were blocked by US hedge fund Coltrane, its largest shareholder.EY sold the business in a 'pre pack' deal to hedge funds and banks, allowing the company to continue trading and protecting its 45,000 UK employees.The company's chief executive Debbie White said at the time: "With a stronger financial platform in place, Interserve will be able to concentrate on delivering value for our customers. The group's transformation programme will continue, focused on improving our value propositions for customers, standardising our operational delivery, making Interserve simpler and more efficient through our Fit for Growth initiatives, and embedding a culture of ownership and openness throughout the group."Interserve is fundamentally a strong business and with a competitive financial platform in place we see significant opportunities ahead as a best-in-class partner to the public and private sector."The FRC is also investigating Grant Thornton over its audit of café chain Patisserie Valerie, which collapsed back in January.