A grand jury will investigate the blockade of a Mississippi River bridge by armed police officers last year who turned back Hurricane Katrina evacuees trying to flee New Orleans.

Orleans Parish District Attorney Eddie Jordan did not say when the grand jury will be convened. He refused to reveal any details of the investigation but said in a prepared statement that he had received a report from the state attorney general's office.

Several hundred evacuees claimed that police from suburban Gretna blocked them as they tried to flee New Orleans for safety on Sept. 1.

Many of the evacuees, who had been stranded at the New Orleans convention center without food and water, said they were told to cross the bridge to be evacuated from the city. But Gretna police confronted them on the bridge and forced them to turn around.

Police later said they blocked the evacuees because there were no supplies or services for them on the other side of the river.

The case raised widespread allegations of racism and spurred two marches across the bridge by national civil rights organizations in the months after the hurricane.