'We felt the loudest boom that you could possibly feel.
"I started seeing pieces of the building falling on my head", Villa told ABC News.
"We got our workout in, picked up the kids, walked out, got in the auto, drove away and as we drove away everything exploded". I probably wouldn't be here, my kids wouldn't be here'.
"A search has been completed of the building itself", Gordon said.
The blast has been reported at The Fountains center in Plantation, Florida.
All the injured had been taken to area hospitals for treatment, he said.
Video from the scene shows an L.A. Fitness gym with windows blown out and debris on the ground.
The explosion shattered windows and damaged nearby buildings.
"There is a closed pizza place place right on the corner but we haven't confirmed it originated there", he said. "I looked outside and it was nearly like the world was ending".
"A huge, huge bang, thump, almost, explosion", he said. "It was nuts, man".
The blast rattled nearby homes and businesses.
Other businesses include a Carrabba's Italian Grill, a Great Clips and Code Ninjas, a national chain where children learn how to create video games.
Michael von Friedrich, 48, of Davie said he was in a Zumba class on the second floor during the explosion.
"Oh yes, I did", she said. But, at the same time, we're just so grateful that no one's hurt.
Gordon said that his department had "an approximate count of about 15 to 20 patients", but had not officially confirmed the number of injuries. "We believe that. That's what it appears to be".
Fire Rescue initially had trouble getting close to the scene because of debris blocking the access roads. "Please do not come to this area if possible", Plantation Police tweeted.
Gordon said Saturday afternoon that authorities "secured the hazards".
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