A portion of the breached levee wall of the 17th Street Canal

U.S. federal prosecutors are conducting a criminal investigation into the levee failures that led to widespread flooding in New Orleans after Hurricane Katrina.

The office of U.S. Attorney Jim Letten says it is examining possible corruption in the flood barriers' design, construction and maintenance.

Mr. Letten said Wednesday that some public officials were found to have "undisclosed conflicts of interest," and that his office is "extremely concerned about those."

New Orleans FBI agent James Bernazzani said federal agents have received numerous tips about possible misconduct related to the levees.

Louisiana state and local officials are also investigating the levee failures. At the peak of the flooding, some 80 percent of New Orleans was underwater.

It took engineers several weeks to dry out the city, most of which sits below sea level.