BUFFALO, United States (AFP) — Emergency crews in New York were scrambling Monday to rescue marooned residents from what authorities called the "blizzard of the century," a relentless storm that has left nearly 50 people dead across the United States and caused Christmas travel chaos.

Blizzard conditions persist in parts of the northeastern US, the stubborn remnants of a massive sprawl of extreme weather that gripped the country over several days, causing widespread power outages, travel delays and at least 49 deaths across nine states, according to official figures.

In New York state, authorities have described ferocious conditions, particularly in Buffalo, with hours-long whiteouts, bodies being discovered in vehicles and under snow banks, and emergency personnel going "car to car" searching for survivors.

The perfect storm of fierce snow squalls, howling wind and sub-zero temperatures forced the cancelation of more than 15,000 US flights in recent days, including nearly 4,000 on Monday, according to tracking site Flightaware.com.

Buffalo — a city in Erie County that is no stranger to foul winter weather — is the epicenter of the crisis, buried under staggering amounts of snow.

"Certainly it is the blizzard of the century," New York Governor Kathy Hochul told reporters, adding it was "way too early to say this is at its completion."

Hochul said some western New York towns got walloped with "30 to 40 inches (0.75 to 1 meter) of snow overnight."

Later Monday, Hochul spoke with President Joe Biden, who offered "the full force of the federal government" to support New York state, and said he and First Lady Jill Biden were praying for those who lost loved ones in the storm, according to a White House statement.

Biden also approved an emergency declaration for the state, the White House said.

The National Weather Service forecast up to 14 more inches of snow Monday, in addition to the several feet that have already left the city buried, with officials struggling to get emergency services back online.