NEW ORLEANS — Federal authorities are investigating allegations that New Orleans police were told after Hurricane Katrina to “take the city back and shoot the looters.”

Police spokesman Bob Young said Friday that federal officials have asked police for information and for permission to interview officers about the alleged orders.

The August 2005 storm flooded 80 percent of the city, knocked out power and police communications and led to widespread chaos. Looters were photographed carrying merchandise from upscale stores, gunfire could be heard in many areas of the city and residents were terrified of lawlessness.

In a documentary this week by Times-Picayune, PBS Frontline and ProPublica reporters, several incidents were cited in which officers claimed they were authorized by police brass to shoot looters after Katrina.

“In response to the printed and televised interviews published, I have been contacted by federal authorities who have initiated a review and inquiry into this matter. Due to this, the NOPD cannot discuss this matter,” Superintendent Ronal Serpas said.

Attorney Eric Hessler said he witnessed an interview in which a police captain said then-Deputy Superintendent Warren Riley told officers to “take the city back and shoot looters.”

Hessler said Capt. Henry Mendoza made the statement this week to two FBI investigators, indicating that the conversation with Riley took place two or three days after Katrina struck on Aug. 29.

Riley refused to comment Friday, but he has previously denied issuing such an order.

The case is one of nine federal investigations of the New Orleans Police Department growing out of Hurricane Katrina.