Protection officer Martiza Matarrita said that many migrants had learned about the caravans via social media and television reports and had not understood what was involved in the trek to the US border.

“Many of them said it was almost an impulse, they didn't stop to think about the risks and the exhausting days of walking,” she said. “They just joined a group of friends or neighbours and joined the caravan.”

Working is what I've done since I was 11. But seeing things as they are, I changed my mind. I think it’s best for me to return to El Salvador - caravan member, Dennis Javier

The UN agency – which said that 62 per cent of those who joined the caravans did so to search for work - also cited the testimony of Dennis Javier, one of the migrants who requested IOM’s support to go home.

“My destination was the US, I was looking for a job,” he said. “Working is what I've done since I was 11. But seeing things as they are, I changed my mind. I think it’s best for me to return to El Salvador.”

More than 450 migrants have been helped back to their countries of origin since 4 November via IOM’s Assisted Voluntary Return programme, which is funded by the US State Department’s Bureau for Population, Refugees and Migration.

According to the UN agency, more than eight in 10 returnees were men and nearly one in three were aged 19-25.

Nearly six in 10 people of those who joined the caravans came from Honduras, almost four in 10 were from El Salvador and around one in 20 were from Guatemala.

25 migrant children flown home so far - IOM

An additional 25 unaccompanied migrant children were helped home by plane, IOM said, adding that in the Mexican city of Tijuana - close to the US border - more than 300 people have also sought the agency’s help to go home.

“IOM is coordinating safe and dignified means of transport for them,” it said in a statement. “Migrants wishing to return are counselled and screened by IOM to evaluate their options prior to making the decision to return.”

In addition to its facilities in Tijuana, IOM also runs information and registration booths in Tapachula, Mexico City, and in Tecun Uman, Guatemala.

To ensure the safe return of the migrants, IOM coordinates with the governments of the returnees, who receive food and psychosocial support at border crossings. When they arrive at reception centres in El Salvador, Honduras and Guatemala, migrants receive hygiene kits and, in many cases, transportation money to get home.

According to IOM, although “a large number” of migrants who had joined the caravans had “muscle disorders, fatigue and malaise…cough and flu”, more than four out of five were in “healthy” shape.

Since 1979, IOM has helped 1.5 million migrants return to their country of origin or residence through its assisted returns scheme.

"A voluntary returns programme is an indispensable part of a comprehensive approach to migration management aiming at orderly and humane return and reintegration of migrants who are unable or unwilling to remain in host or transit countries and wish to return voluntarily to their countries of origin," said Marcelo Pisani, IOM Regional Director for Central America, North America, and the Caribbean.