PLANTATION, Fla. (AP) — A vacant pizza restaurant exploded Saturday in a thundering roar at a South Florida shopping plaza, injuring more than 20 people as large chunks of concrete flew through the air.

The blast flung debris widely along a busy road in Plantation, west of Fort Lauderdale. The restaurant was destroyed, and nearby businesses and cars were damaged. Though firefighters found ruptured gas lines afterward, authorities said it was too early to determine a cause.

"We thought it was thunder at first, and then we felt the building shake and things started falling. I looked outside and...