Firefighters found a ruptured gas line, but could not yet confirm what had caused the strip-mall explosion.
Police are investigating the scene at a Florida shopping center after an explosion in Plantation injured 21 people, two critically, Saturday.
Video footage showed the force of the blast blew out several windows at an 'L.A. Fitness' gym, sending patrons running for the exits.
Firefighters found a ruptured natural gas line at the center, but authorities said the cause of the explosion in Plantation, Florida, about six miles west of Fort Lauderdale, was still under investigation.
A pair of shoppers suffered severe injuries and were transported to a trauma center at a nearby hospital, Plantation Deputy Fire Chief Joel Gordon, reported.
“We’re relieved - the injuries are not as severe as we thought they would be … This could have been a lot worse,” he told reporters.
In an interview with Sun-Sentinel, witness Evan Hoffman said he heard “a huge, huge bang, thump, almost, explosion. It started shaking back and forth and the roof tiles started crashing down and the power went out.”
Another witness, Jesse Walaschek — father of three — told CNN he barely avoided the catapulting concrete from the explosion. Walaschek, together with his family, had just left the fitness center when the incident occurred.
"We felt the loudest boom that you could possibly feel. I looked in my rear view mirror and it was just a dust cloud. Had we walked out of that gym 15 seconds later, I would've been getting my kids in the car when it went off. I probably wouldn't be here, my kids wouldn't be here," he said.