GREENVILLE, S.C. -- A single storm that developed over the Haywood Mall area Sunday knocked down signs, broke off tree limbs and snapped power lines.

Some witnesses said they saw a tornado, but meteorologists said it was most likely a downburst.

Downburts occur when upper-level winds can no longer keep water inside a cloud. The water falls to the ground at a high speed. As the rain moves toward the ground, it forces the strong winds to the ground, as well. This usually results in heavy rain and damaging winds greater than 60 mph.

Patrons of the Chili’s Grill and Bar on Haywood Road said they were moved to the kitchen to take cover during the storm. They saw the rain coming down “sideways,” and the wind blowing extremely hard, they said.

Police closed parts of Haywood and Congaree roads while they removed the downed trees and repaired power lines. All roads were back open as of Monday morning.

After the storm, Duke Energy reported more than 1,000 customers without power. That numbered had dropped to more than 570 by 10 a.m. Monday.

Power crews reminded residents that if they find a power line down in their area, stay away from it and call their local utility company immediately.