(Reuters) - A fire engulfed several blocks of boardwalk and businesses on Thursday in Seaside Park, New Jersey, a shore town that was still rebuilding from damage caused by Superstorm Sandy.

New Jersey Governor Chris Christie said 20 businesses had been damaged in a six-block length of the boardwalk and firefighters were struggling to contain the blaze.

"I told my staff, 'I feel like I want to throw up,'" Christie told a televised news conference, referring to the effort to rebuild after the October 2012 storm. "It is just unthinkable."

The cause of the fire was unknown, Christie said. Some firefighters suffered minor injuries, he added.

John Saaddy, a business owner in nearby Seaside Heights, New Jersey, told CNN the fire had spread by racing through a "fire highway" under the boardwalk.

Standing on the scene amid clouds of billowing black smoke, Christie called the blaze an "unthinkable situation."

"We have firefighters and trucks from all around New Jersey working together," Christie said.

Christie said that winds were gusting at 30 to 40 miles per hour (48 to 65 km per hour) as he spoke, stirring up the flames. A major rainstorm heading to the shore should help douse the fire, he said.

The fire drew a massive response, with 35 engine companies and 15 ladder reporting. Crews tore up the boardwalk at Lincoln Avenue, and dug a 20-foot (6-meter) trench, Christie said.

"That's where firefighters are making their stand right now to stop the spread any further north on the boardwalk," Christie said.

(Reporting by Ian Simpson in Washington and Dave Warner in Philadelphia; Editing by Scott Malone, Ken Wills and Lisa Shumaker)