OCRACOKE, N.C. — Four people working on Independence Day fireworks shows were killed by explosions, three of them by a single blast that rocked this remote village on the Outer Banks islands.

In addition, a pedestrian bridge collapsed in Indiana as fans were leaving a fireworks show, injuring 25 people. Authorities said Sunday the crowd had overloaded the bridge.

The blast at Ocracoke came as workers were unloading fireworks Saturday from a truck at the Anchorage Marina, shaking homes and businesses across the southern end of Ocracoke Island and rattling residents and tourists.

Agents from the Bureau of Alcohol, Tobacco, Firearms and Explosives were on the island off the North Carolina coast Sunday investigating the blast.

Dock master Robert Raborn was about 200 yards away from the truck and said the explosion was one of the loudest things he had ever heard.

“It was like 40 minutes worth of fireworks going off in four seconds,” Raborn said.

The third victim died late Saturday at Pitt County Memorial Hospital in Greenville, said Hyde County spokeswoman Jamie Tunnell. Two other workers were injured; their conditions were not immediately released.

All five worked for Melrose South Pyrotechnics near Rock Hill, S.C. The company said it had sent a representative to work with investigators.

Pennsylvania state police fire marshals were investigating the death of a worker Saturday at the start of the grand finale of fireworks at Quakertown’s Memorial Park.

Quakertown Police Chief Scott McElree said authorities immediately halted the show and evacuated part of the park in eastern Pennsylvania.

Authorities did not immediately identify the man’s employer.

At Merrillville, Ind., the collapse of a wooden pedestrian bridge dropped at least 50 people into a lake Saturday night and injured about 25 of them, police said. None of the injuries was life-threatening, authorities said.

The collapse occurred at Hidden Lake Park in Merrillville, about 45 miles southeast of Chicago, as spectators were leaving a fireworks display at about 10 p.m.

The wooden, cable-suspended bridge could handle about 40 people at a time but as many as 80 were on it when it gave way, said Ross Township Trustee John Rooda, who attended the fireworks show. The township operates the park.

“The problem is it was overloaded,” Rooda said. Merillville police officers were stationed at either end of the 90-foot bridge to control the number of people, but the crowd “rushed” the officers, Rooda said Sunday.

Home fireworks shows also were dangerous.

In Wisconsin, Jefferson County Sheriff Paul Milbrath said a 12-year-old boy suffered a head injury when he was hit by one of the pyrotechnics fired at a July Fourth party. The boy was taken to a hospital in Milwaukee; his name and condition weren’t released.

The Callahan Eye Foundation Hospital in Birmingham, Ala., treated five patients who were hurt in fireworks accidents, spokeswoman Gail Short said Sunday. Short cited federal privacy laws in declining to give details.