The Federal Reserve Bank of St. Louis said hackers succeeded in directing traffic from its popular economic-data websites in April to phony pages where they may have attempted to steal user names and passwords.

"Computer hackers manipulated routing settings" on April 24 sending "web traffic that day to rogue webpages they created to simulate the look of the St. Louis Fed's website," the bank said in a statement on Monday.

The bank, which operates the Federal Reserve Economic Data service known as FRED, notified active users of its sites as a precaution that they could have become "exposed to vulnerabilities" such as having stolen user names and passwords.

"The St. Louis Fed's website itself was not compromised," the bank said.

Users of the sites are being asked to change passwords.