By Adam Fenster

ELMIRA, New York (Reuters) - Two people were dead and more than 100,000 homes and businesses in New York, Ohio and Pennsylvania were without electricity Friday morning after severe thunderstorms swept through the region late Thursday.

The storms spawned a tornado that touched down in Elmira, New York, toppling trees and tearing off roofs, the National Weather Service said.

Officials in Pennsylvania and New York reported two storm-related deaths.

A woman who was camping in Genesee, Pennsylvania, near the New York State line, was killed when she took refuge from the storm in her car and a tree then fell on it, John Hetrick, director of emergency services for Potter County, said.

In New York City, a 61-year-old man in Brooklyn's Cobble Hill neighborhood was killed when scaffolding at a church collapsed on him as the storm passed through near 8 p.m., police said.

"It's possible that lightning struck the top of the roof, causing some bricks to fall on top of the scaffolding, causing the scaffolding to fall on top of the victim," a police spokesman said.

In Elmira, the city's east side took the biggest hit from the tornado. In one four-block neighborhood, most homes had trees toppled upon them, street signs were bent in half and tree trunks had debris wrapped around them. Several cars were crushed by downed trees.

One two-story brick building had most of the second story torn off in the storm.

On Friday morning, most power remained out for the city's 29,000 residents.

Meteorologists said 70-mile-per-hour (113-kph) winds were reported in parts of Ohio, Kentucky, Pennsylvania and Oklahoma.

As the storms sent black, menacing clouds rolling across some cities, hail ranging from the size of a dime to a quarter fell in some areas of Pennsylvania, AccuWeather.com said.

Pennsylvania accounted for a majority of those still without power, with more than 85,000 customers in the dark early Friday, according to electric companies serving the region.

Roughly 34,000 people in New York were without power, most of them in the southern tier region near Elmira, according to NYSEG. About 13,500 customers in eastern Ohio were still offline, according to AEP Ohio.

The storms formed along a cold front stretching from the Northeast into the Ohio Valley, bringing the threat of damaging winds, hail and tornadoes, according to the Weather Channel.

The storm activity forced the cancellation of over 900 flights on Thursday, according to FlightAware, a Texas-based company that tracks the status of flights. The highest number of cancellations was at LaGuardia Airport in New York.

(Additional reporting by Kevin Gray and Alex Dobuzinskis; Writing by Dan Burns; Editing by Eric Walsh)