(CNN) -- New Jersey Gov. Chris Christie called a fire raging through boardwalk buildings Thursday an "unthinkable situation" as firefighters continued to fight the high flames and black smoke in Seaside Park, New Jersey.
Christie said 35 engine companies, 15 ladders and 400 firefighters remained on the scene Thursday evening.
So far, about 20 businesses have been burned and damaged over six blocks. Some embers hit a condominium, but it was quickly put out, Christie said.
Several firefighters have sustained minor injuries, including heat exhaustion and smoke inhalation, Christie said.
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The fire was still burning along Ocean Terrace Avenue between Stockton Avenue and Lincoln Avenue Thursday evening.
Christie said he was notified of the fire shortly after 3:30 p.m. ET.
A cause has not been determined. The damage is almost entirely on the boardwalk, Christie said.
Fire personnel dug a 20-foot trench on Lincoln Avenue; "that's where firefighters are making their stand right now," Christie said. Brisk winds are spreading the fire, Christie said.
"The destruction south of Lincoln Avenue, it's complete," Christie said Thursday.
"I said to my staff, I feel like I want to throw up, and that's me. After all the effort and time and resources that we've put in to help the folks in Seaside Park and Seaside Heights rebuild. To see this going on, as I said at the top, is just unthinkable."
The famous boardwalk of Seaside Heights was thrown into the public eye shortly after Superstorm Sandy tore its famous Jet Star roller coaster into the water. The coaster was removed from the ocean in May, shortly before the boardwalk reopened for business.
The FunTown Pier was destroyed by Sandy and partially reopened this summer.
Seaside Heights Mayor Bill Akers told CNN in May that rebuilding the boardwalk cost $8 million. The total cost for Sandy repairs in Seaside Heights was $16 million.
Christie explained that fire troops were experiencing water supply challenges because of damage to the system post Sandy, and that teams were drawing lines from Barnegat Bay.
CNN affiliate KYW reported that the fire started at Kohr Brothers frozen custard shop on the FunTown Amusement Pier around 2:15 p.m. ET. The fire escalated to six alarms shortly before 4 p.m. ET, according to the same affiliate.
Jersey Central Power and Light spokesman Ron Morano said their crews are in the area and that he is not aware of any outages due to the fire.