NEW ORLEANS, Louisiana (AP) -- Federal prosecutors said they are conducting a criminal investigation into the levee failures that swamped New Orleans.Federal investigators are looking into the possibility of corruption in the design, construction and maintenance of the flood barriers, U.S. Attorney Jim Letten said.Letten said Wednesday that his office began the investigation the week after Hurricane Katrina. The August 29 hurricane, and subsequent canal breaches left about 80 percent of New Orleans under water, killing hundreds of residents and stranding thousand more."The scope of our interest is very broad," Letten said.He said some officials were found to have undisclosed conflicts of interest, and "we're extremely concerned about those." He would not give details.James Bernazzani, FBI agent in charge in New Orleans, said agents have received numerous tips about possible malfeasance.Other investigations are being conducted by Louisiana's attorney general, who is looking into whether poor construction or design flaws played a role in the failures, and the New Orleans district attorney, who raised the possibility that faulty materials were used in the flood walls.Earlier this week, Attorney General Charles Foti said he wants to know whether poor construction or design flaws contributed to the failure. The Orleans Parish district attorney's office also confirmed it started a preliminary investigation into the materials used in the flood walls. It is determining whether a grand jury should be impaneled. The office is requesting copies of pertinent reports and is aware of recent congressional testimony about possible malfeasance in flood wall construction, said Leatrice Dupre, spokeswoman for District Attorney Eddie Jordan. Copyright 2005 The Associated Press. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed.