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At least 28 people were killed in New York state, most of them in Buffalo, bringing the total number of victims of a severe winter storm sweeping North America to 56.

A state official said some people were stuck in cars for more than two days during what was described as "probably the worst storm" of their lives.

Meteorologists warned that more snow, up to nine inches (23 centimeters), could fall in parts of the state through Tuesday.

US President Joe Biden has approved an emergency declaration allowing federal aid for New York State. "My deepest sympathy goes out to those who lost loved ones this weekend," he wrote on 

"It's (like) going to a war zone, and the sight of vehicles on both sides of the roads is shocking," she added.

It said many emergency services vehicles were unable to reach the hardest-hit areas or got stuck in the snow.