OCRACOKE, N.C. (July 4) - A truckload of fireworks exploded Saturday morning on a dock at a remote North Carolina island, killing two workers and critically injuring three others preparing for an Independence Day celebration, authorities said. The explosion shook homes and businesses and was heard across a village on the southern end of Ocracoke Island, which is the only inhabited part of the 15-mile spit of land, accessible only by boat. Dock master Robert Raborn noticed the workers unloading the truck from the Anchorage Marina about 200 yards away and described the explosion as one of the loudest things he has ever heard. "It was like 40 minutes worth of fireworks going off in four seconds," Raborn said. Hundreds of tourists and residents streamed down to the south end of the island to see what was going on, Raborn said. Three medical helicopters took the injured employees to hospitals, Hyde County spokeswoman Jamie Tunnell said. One worker died at the scene and the other died about six hours later at a hospital. Another worker was in fair condition at a burn center in Chapel Hill, about 180 miles away, said Clinton Colmenares, spokesman for the North Carolina Jaycee Burn Center at the UNC Medical Center. The other injured workers were taken to Pitt County Memorial Hospital in Greenville, but their conditions were not released. Authorities have not released the names of the workers, four men and one woman, or suggested what might have caused the blast. Agents from the Bureau of Alcohol, Tobacco, Firearms and Explosives and other federal officials are coming to the island to investigate. The crew worked for Melrose South Pyrotechnics near Rock Hill, S.C. The company said in a statement it had sent an official to work with investigators. The explosion stopped ferries to the island for a few hours, but service was restored later Saturday. Bob Chestnut, owner of the Ride the Wind surf shop, said the explosion reminded residents of how isolated they are — hours away from any major city. There is a .