NEW ORLEANS (AP) — A grand jury has declined to bring criminal charges against anyone in the 2005 police blockade that kept hundreds from crossing the Mississippi River to safety after Hurricane Katrina flooded New Orleans, the district attorney’s office said Wednesday.

Dalton Savwoir, a spokesman for New Orleans District Attorney Eddie Jordan, confirmed that the grand jury declined to bring charges and said the panel was expected to deliver its decision to a state judge on Wednesday afternoon.

Police from the Jefferson Parish city of Gretna have called a 2 p.m. CDT news conference to discuss the case.

The storm hit Aug. 29, 2005, flooding 80 percent of the New Orleans. Thousands were stranded at the Louisiana Superdome and Morial Convention Center with no power, and short supplies of food and water. There were widespread reports of violence and looting.

Gretna Police Chief Arthur Lawson has acknowledged that his officers fired shots into the air during the blockade in an attempt to quell what he described as unrest among the evacuees. Lawson and other suburban New Orleans law enforcement agencies have said the blockade was needed to keep order because their jurisdictions were also heavily damaged and shelters and emergency agencies were under tremendous stress.

Savwoir wouldn’t disclose any details of the grand jury’s probe, including who the possible targets of its investigation were.

‘‘We can’t discuss the grand jury process at all,’’ he said.

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. The state Attorney General’s office investigated and turned its information over to District Attorney Eddie Jordan, who announced in August 2006 that there would be a grand jury probe.

Katie Schwartzmann, a lawyer for the New Orleans chapter of the American Civil Liberties Union, said assault charges may have been warranted if officers had fired shots over the heads of unarmed citizens.

The ACLU filed a public records request with Jordan’s office, seeking copies of police reports and other documents linked to the probe of the blockade. Jordan’s office refused to turn over the records, citing the ongoing investigation.

‘‘We just wanted to see it investigated fully and see the criminal justice system respond,’’ Schwartzmann said.