The Financial Services Authority is investigating Royal Bank of Scotland's (RBS) acquisition of ABN Amro and its £12bn rights issue.The inquiry was mentioned in a footnote in RBS's interim results."In April 2009 the FSA notified the group that it was commencing a supervisory review of the acquisition of ABN AMRO in 2007 and the 2008 capital raisings. The group and its subsidiaries are co-operating fully with this review," RBS said in the note.RBS, along with Santander and Fortis, bought Dutch bank ABN Amro for €70bn in October 2007, beating Barclays for the company. The bank was criticised for continuing with the deal despite the beginning of the financial crises.Six months after the acquisition, RBS launched a £12bn rights issue to deal with its financial problems but it was not enough and the bank had to be rescued by the government.