JACKSONVILLE, Fla. (AP) – Federal accident investigators have returned to shore with sunken freighter El Faro’s “black box,” but say it could be weeks before they know if it will help them understand what happened in the hours before the ship sank. The Florida Times-Union reports that crews on Friday arrived at Naval Station Mayport in Jacksonville with the device, which was recovered from about 3 miles below the sea earlier in the week. The National Transportation Safety Board’s Brian Curtis says investigators won’t know if the voyage data recorder is useful until they examine it at their lab in Washington. The recorder could hold 12 hours or more of audio from the bridge of the 790-foot ship, which sank Oct. 1 while sailing from Jacksonville to Puerto Rico. All 33 aboard died.