The Serious Fraud Office (SFO) is investigating computer giant Hewlett-Packard's claim that it was duped when it bought UK-based business software maker Autonomy, according to regulatory documents.
The SFO probe is the latest fallout from a deal that has saddled Hewlett-Packard with huge losses and depressed its stock price.
The US Justice Department started looking into the matter last year, shortly after HP accused Autonomy employees of fabricating sales in an alleged ruse that drove up the company's sale price.
Autonomy's founder and former chief executive Mike Lynch has strenuously denied HP's claims and demanded that the company provides more evidence to support its allegations.
HP, based in Palo Alto, California, has repeatedly said that it is co-operating with legal authorities looking into the claims.
It bought Cambridge-based Autonomy for about $10bn (£6.7bn) in 2011 and then wrote off $8.8bn (£5.9bn) of that late last year in a move that stunned Wall Street.
At least eight lawsuits have been filed by HP shareholders claiming that the company's board and management botched the Autonomy deal.