WASHINGTON (AFP) - A massive early snowstorm pounded the Buffalo, New York, area on Tuesday, dumping record snowfalls, trapping people in cars and homes, and killing four people, the authorities said.

Even in a city famous for blizzards that roar off Lake Erie just to the west, this one stunned locals; it even featured the unusual phenomenon of "thunder snow". Many areas south of the city, which is near Niagara Falls, were socked with over 1.5m in less than 24 hours.

"Some parts of our county are going to receive a years worth of snowfall in three days," Erie county executive Mark Poloncarz told local media adding that three people have died from apparent heart attacks while shoveling snow, and another while pushing a trapped car. With a driving ban in effect, local media reported at least one person was trapped after a roof collapsed into a home.

"This will be a historic event," weather forecaster Dave Zaff said. "Absolutely. It is a historic event."

Officials also urged older residents not to try to shovel the heavy white stuff.

Highway crews were between a rock and a hard place; snow plows generally cannot operate effectively with snowfalls over 1m.

Some first responders carried gurneys down snowed-in streets because ambulances could not get through.

Other paramedics used snowmobiles on rescue calls, since streets were impassible.

The National Guard has been called out to assist, Governor Andrew Cuomo said.