It was here that the Salvadoran refugee Oscar Alberto Martinez Ramirez, 25, and his 23-month-old daughter, Valeria, arrived to claim asylum in the United States two months ago.

His black shirt is hiked up his chest with the girl's head tucked inside, and her arm draped around his neck suggesting she clung to him in her final moments.

The image, which showed the girl still holding on to her father, lying face-down in the water, was taken by journalist Julia Le Duc and published by Mexican newspaper La Jornada, and it has served to highlight the high risk migrants face on the perilous journey to the US.

The family decided to make the risky crossing after waiting two months to receive political asylum from the U.S.at a detention facility in Matamoros, Mexico, local La Jornada daily reported, citing Martinez's wife. Ramirez swam across the river with his 23-month-old daughter, Valeria, in tow.

Amid tears and screams, Tania Vanessa Avalos, Mr Ramirez's wife, reportedly described the drowning to police officers at the scene. Martinez, while trying to grab Valeria, got swept away due to the water current.

"Ever since he first told me that they wanted to go, I told him not to", Ramirez said, recalling conversations with her son. "He put her in his shirt and I imagine he told himself, "I've come this far" and chose to go with her".

However, the global bridge was closed and they chose to try to swim over the river to Brownsville, Texas, with their tiny daughter.

In the municipality of San Martin in El Salvador, his mother Rosa Ramirez wept as she held her granddaughter's favourite doll and stuffed animal. "They hoped to be there a few years and save up for the house".

Salvadoran Minister of Foreign Affairs Alexandra Hill said the government is working with Mexican authorities to repatriate the remains.

After leaving their home in El Salvador in April, Martinez and his wife and daughter spent two months in a shelter in Guatemala, before crossing into Mexico.

The US-Mexican border continues to be a unsafe place for migrants.

The shocking image captured Monday was a grim reminder of the unsafe journey migrants take to get to the United States.

A harrowing photo of a man and his young daughter who drowned on the U.S. -Mexico border has brought global attention to the dangers for a wave of mostly Latin American migrants travelling north, with Pope Francis on Wednesday expressing "immense sadness" at the deaths.

The pair from El Salvador drowned Sunday in the Rio Grande as they were crossing from Mexico into Texas near Brownsville.

US officials told Congress on Wednesday that they did not have adequate staffing and facilities to adequately handle the surge of migrants seeking asylum and made it harder to intercept drug smuggling and staff customs operations at ports of entry.

It comes after US President Donald Trump announced last weekend that he would delay raids by Immigration and Customs Enforcement (ICE) targeting families that have received deportation notices.

Meanwhile, Mexico is stepping up its own crackdown on immigration in response to USA pressure, with much of the focus on slowing the flow in the country's south.