AMSTERDAM, NY — A tornado that damaged homes and businesses near Albany arose from a string of violent thunderstorms a week after Tropical Storm Irene flooded the region.

The tornado, about a half-mile wide, was on the ground for more than 10 minutes Sunday evening, according to Steve DiRienzo, a National Weather Service meteorologist.

Amateur video posted online shows a dark funnel cloud knocking down trees as it crosses the New York Thruway.

DiRienzo said it hit at about 5:20 p.m. and swirled east about four miles along the Mohawk River, from the town of Amsterdam into Schenectady County’s hilly West Glenville.

Estimates of wind speeds were not immediately available, but trees and power lines were knocked down, roofs and siding torn off and windows blown out. Thirty to 40 homes and businesses reported some damage.

There were no reports of serious injuries, however, prompting Amsterdam Town Supervisor Tom DiMezza to point out that it could have been “a lot worse.”