The Navy says a fire aboard the USS George Washington aircraft carrier last month was made worse by improperly stored flammable materials.

In response to the fire, the Naval Sea Systems Command last week asked the Navy's nearly 300 ships to verify they've properly stowed flammable and combustible materials.

The U.S. Pacific Fleet says officials still haven't determined what caused the fire, but the ship will need structural and mechanical repairs.

One sailor suffered minor burns and 23 others complained of heat stress in the May 22 fire. They have all returned to duty.

The fire was spotted near the auxiliary boiler room and air conditioning and refrigeration space in the rear of the ship. The safety of the ship's nuclear reactor wasn't threatened.