Snowstorm strikes north-eastern United States

The north-eastern US states of New York, New Jersey, Pennsylvania and Virginia have declared states of emergency as a huge winter storm sweeps in, bringing heavy snow.

The US National Weather Service issued blizzard warnings from eastern Pennsylvania to south-west Maine.

Schools are closed and thousands of flights have been cancelled.

The conditions caused German Chancellor Angela Merkel to postpone a trip to Washington to meet President Trump.

It has now been rescheduled for Friday.

Authorities in the state of New Hampshire say a 16-year-old girl died after losing control of her car and crashing into a tree around 07:00 local time on Tuesday morning.

The girl, whose name is being withheld, was transported to hospital where she was pronounced dead.

With winds of up to 60mph (100km/h), the storm is causing severe disruption for commuters across many parts of the north-east, and authorities in several states are advising residents to stay off the roads.

In all, about 50 million people across the country have been warned about the severe weather.

New York's mayor warned residents like this man that they won't see pavement 'for quite a while'

Ploughs work to clear the runways at Newark International Airport

There has also been heavy snow in other parts of the country. In the state of Wisconsin, four people aged over 60 died in separate incidents while shovelling snow, according US media.

Why do so many people die shovelling snow?

House in New York state encased in ice

Less snow than originally anticipated is now expected to fall in New York City, with the forecast downgraded to between 4 and 8 inches (10-20cm) by the US National Weather Service.

However, up to two feet of snow was still expected in other parts of New York state, the service said.

"During its height we could see snowfall rates of 1-3 inches (2.5-7.6cm), even up to four inches per hour," said Alan Dunham, a meteorologist based in Taunton, Massachusetts.

More than 6,800 flights have been cancelled, tracking service FlightAware reported, with airports in New York, Washington, Boston, Baltimore and Philadelphia worst hit.

Two US Congressmen from Texas - one Democrat and one Republican - decided to make the drive back to Washington from their home districts near the southern border together, after their flights were canceled.

Representatives Beto O'Rourke and Will Hurd are taking turns driving, as the other films Periscope and Facebook live broadcasts, which they have dubbed a "cross country bipartisan townhall".

In New York City, Mayor Bill de Blasio is praising the city's "cowboy officer" who wrangled two ponies after they got loose from their enclosure and began roaming the streets of Staten Island.

NYPD chief of patrol Terence Monahan says the officer used tow truck straps to tie the animals to a street pole until backup could arrive to transport them back to their stables.

The NYPD special operations unit tweeted a photo of the ponies.

Skiers explore the fresh snow in New York's Central Park

New York city is experiencing freezing conditions

Declaring a state of emergency, New York Governor Andrew Cuomo said commuters should expect road closures, delays and cancellations.

New Jersey Governor Chris Christie also declared a state of emergency and ordered all state employees not involved in the response to stay at home.

Wall Street's bull and girl statues, covered in snow in New York City

In Canada, Ontario, Quebec and the Maritime provinces are also bracing for the storm, and numerous flights have already been cancelled and delayed.

Police responded in the afternoon to a multi-vehicle collision in snowy conditions on Highway 401 in southern Ontario. One of the vehicles involved is leaking a "highly toxic" substance, according to police.

People stranded are being asked to remain in their cars until they can be safely evacuated from the area as a precaution.

The winter storm follows a spell of unusually mild weather in the north-eastern US, with last month being the second warmest February since record-keeping began in 1895.

In 2016 New York experienced the biggest snowstorm in the city's history, with a record 27.3 inches falling on Central Park in 24 hours.

The blizzard brought parts of the north-eastern states to a standstill, and left 18 people dead.