Updated

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 U.S. Attorney's office in New Orleans and FBI spokeswoman Sheila Thorne refused to comment on the investigation.

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 New Orleans stores, gunfire could be heard in many areas of the city and residents were terrified of lawlessness.

In a documentary this week by reporters from The Times-Picayune, PBS Frontline and ProPublica, 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 in a prepared statement.

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 the conversation with Riley took place two or three days after Katrina struck on Aug. 29.

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

Reporters for the Frontline report were shown a portion of a grainy videotape in which Capt. James Scott told officers, "We have authority by martial law to shoot looters."

There is no provision under the Louisiana Constitution for martial law, although the governor can declare a state of emergency, said Loyola law professor Dane Ciolino said.

"The police chief clearly had no power whatsoever to declare any sort of martial law," Ciolino said. "And the principles and rules on the use of deadly force can't be changed by the police chief, the mayor or the governor."

Eleven civilians were shot by police in the week following Katrina, although just one of them was said to have been looting.

The case is one of at least nine ongoing federal investigations of the New Orleans Police Department, growing out of Hurricane Katrina, that have resulted in charges against 18 current or former officers.