Nearly 250 migrant children have been relocated to children's shelters from an overcrowded Texas border patrol station where attorneys said they had been held for weeks in dirty conditions without adequate food and water.

Evelyn Stauffer, a spokeswoman for the Department of Health and Human Services (HHS), said 249 children from the facility at Clint, Texas, were being transferred to shelters run by the agency by today.

Attorneys last week raised alarm after they were given access to the Clint station near El Paso and said they had found more than 300 children detained in squalid conditions.

The group of lawyers said they saw toddlers without nappies being cared for by unrelated children.

Detained children lacked adequate food, clean clothes, toothbrushes and showers and some children slept on concrete floors, they said.

The conditions were first reported by the Associated Press.

Just 30 children remained at the facility near El Paso yesterday, according to Elizabeth Lopez-Sandoval, spokeswoman for Representative Veronica Escobar.

Children not sent to the HHS shelters were being moved to a tent facility designed for family detention, Ms Lopez-Sandoval said.

US law requires children who cross the border without a parent or legal guardian to stay in border patrol's short-term holding facilities for no longer than 72 hours and to be moved to HHS shelters as quickly as possible.

Ms Stauffer said children were waiting too long in the border facilities, which are "not designed to care for children."

"This is a direct result of the unprecedented number of arriving children," she said.

Ms Stauffer said the Department of Homeland Security (DHS) had referred nearly 10,000 children to HHS in May, one of the highest monthly totals in the history of the program.

The attorneys visited the Clint facility last week to monitor compliance with the Flores agreement, a decades-old legal settlement that establishes how long migrant children can be detained and the conditions of their detention.

Last week, the government argued in federal court that it meets the standard of providing "safe and sanitary" conditions for migrant children without providing toothbrushes and soap.

Seven migrant deaths reported in 'extreme heat' at US border

Meanwhile authorities in Texas reported seven migrant deaths  yesterday, including those of a woman, two babies and a toddler, showing the danger of extreme summer heat as Central American families surge across the US-Mexico border.

The woman and three children may have been dead for days before they were found by US Border Patrol near the Rio Grande in South Texas on Sunday, according to a local law enforcement official, who asked not to be named.

They are thought to have died from heat exposure anddehydration in an area about 29km east of McAllen.

To the west, US Border Patrol agents in the Del Rio area recovered the bodies of two men on ranchland near Carrizo Springs after anonymous calls on 19-20 June alerted them to lost migrants, the agency said in a statement.

Another decomposed body was found 20 June on the riverbankof the Rio Grande near Normandy.

"The extreme temperatures during this time of year can be fatal," said Del Rio Sector Chief Patrol Agent Raul Ortiz.

Arrests of undocumented migrants reached their highest monthly level since 2006 in May, with more than 60% of those apprehended either children or families, many seeking asylum.

The Trump administration has set limits on how many people can claim asylum each day at ports of entry.

With months-long waits for interviews, migrant families are instead attempting sometimes risky border crossings to make their claims.

Smugglers put migrants' lives at risk by dropping them off in desolate areas or sending them across the Rio Grande in makeshift rafts.

Increased fencing and security in many areas means migrants who have been deported, and are seeking to evade capture, oftentake dangerous routes to re-enter the United States.

A six-year-old girl from India died earlier this month from heat stroke in western Arizona after smugglers left a group of migrants in a remote desert location.

Three children and a Honduran man are believed to have diedin April when their raft overturned on the Rio Grande near DelRio. Water rescues at the popular crossing point have soared.

Border Patrol reported 283 migrant fatalities on the border in 2018. Human rights activists say the number is far higher as the remains of many migrants are never found and the agency's data does not include all deaths registered by local authorities.