US financial regulators have demanded information from US banking giant Citi about the sale of its auction-rate securities, the latest major investment firm to have been told to hand over information about the sale of these troubled securities, according to media reports.

Citi disclosed in a regulatory filing that the Securities and Exchange Commission and other regulators have subpoenaed information from the bank about the sale of its auction-rate securities.

Citi said in the filing that officials are investigating whether federal securities laws were violated during the sales of the securities.

Auction-rate securities have their interest rates set at periodic auctions, depending on the submitted bids. The investments were once considered safe, but the market collapsed in February amid turmoil in the credit markets.

Citi is the latest bank to disclose regulators are seeking information on its sales of auction-rate securities. In May, Wachovia disclosed it too has received requests from the SEC about auction-rate securities sales.

Last month, New York Attorney General Andrew Cuomo sued Swiss banking group UBS, accusing it of fraudulently promoting tens of billions of dollars of auction-rate securities as safe when it knew a crisis was brewing. Merrill Lynch has also been sued by regulators in Massachusetts.

In its regulatory filing, Citi said it is facing several individual and class action lawsuits related to the marketing, sale and underwriting of its auction-rate securities.