At least four people have been killed in Spain, where strange snowstorms have caused the largest snowfall in decades, with forces deployed to rescue motorists trapped in travel chaos in the capital, Madrid.

Thousands of people have been stranded at railway stations and airports, with services canceled due to winter conditions.

In Madrid, authorities activated Red Alert for the first time since the system was introduced four decades ago, and authorities sent the army to help 1,500 people stuck in vehicles on everything from small roads to main roads.

More than 50 cm (20 inches) of snow fell in the capital – the highest number recorded in a 24-hour period since 1971, according to the National Weather Agency AEMET.

The Interior Ministry said Madrid had found a 54-year-old man dead under a pile of snow.

Police also reported the death of a homeless man due to hypothermia in the northern city of Zaragoza.

Meanwhile, a man and a woman drowned after their car washed away when a river overflowed its banks near Malaga in southern Spain.

In response to the deaths, King Philip VI and Queen Letizia tweeted: “The royal family wishes to express its grief for the victims of the storm … and requests extreme caution against the dangers of accumulating ice and snow.”

Interior Minister Fernando Grande Marlaska urged Spaniards to avoid all but essential travel.

“We are facing the heaviest storm in the past 50 years,” he said.

AEMET has warned that some areas will receive more than 24 hours of continuous snowfall due to the unusual combination of a cold air mass stagnant over the Iberian Peninsula and the arrival of warm storm Philomena from the south.

The agency said that the storm is expected to move in the northeast of the country throughout Saturday, but it is expected to be followed by a cold wave.

Transport Minister Jose Luis Abalus warned that “snow will turn into ice and we will enter into a situation that may be more dangerous than what we have at the moment.”

“The storm has exceeded our most pessimistic expectations,” added Abalus.

Carlos Novello, head of the Madrid Emergency Agency, described it as a “critical situation” and added: “We ask all those who remain trapped to be patient, and we will reach you.”

The airport operator AENA said Adolfo Suarez Madrid-Barajas International Airport, the main gateway in and out of the country, will remain closed throughout the day.

The railway company Renfe said all trains in and out of Madrid and roads between the south and northeast of the country had stopped.

The storm had caused serious disruption to – or closed – more than 650 routes by Saturday morning, according to Spanish transit authorities, who urged people to stay home and avoid unnecessary travel.

The winter weather even halted the country’s soccer league, as some teams were unable to travel for matches.

A trip to Madrid carrying players with league leaders Athletic Bilbao was forced to return to Bilbao airport, while second-placed Real Madrid were unable to take off in their match against Osasuna.

The Castilla-La Mancha and Madrid regions, home to 8.6 million people in all, announced the closure of schools on at least Monday and Tuesday.