More than 100 migrant children have been returned to a Texas border station just a day after being moved out, a US border official has confirmed.

Some 250 migrant children were transferred from the overcrowded station following a scathing report on its conditions.

Lawyers given access by a judge said the children were “severely neglected”.

Amid the controversy over detained migrant children, America’s top border official said he was stepping down.

A Customs and Border Protection (CBP) official confirmed to the BBC on Tuesday that about 100 migrant children were returned the facility.

The agency also confirmed that its acting commissioner, John Sanders, would be leaving his role on 5 July.

The New York Times reports the children were transported back to the station after it had made changes to alleviate its overcrowding. They had been held at the facility for weeks.

It comes as the number of migrants apprehended at the border surged in May to the highest level since 2006.

What were the conditions like?

One of the lawyers who visited the Clint facility in Texas told the BBC that children were “locked up in horrific cells where there’s an open toilet in the middle of the room” where they ate and slept.

“There was nobody taking care of these children… they were not being bathed on a regular basis,” Prof Warren Binford of Williamette University in Oregon said.

“Several hundred of the children had been kept in a warehouse that was recently erected on the facility grounds.”

“The cells are overcrowded… there’s a lice infestation there, there is an influenza outbreak. Children are being locked up in isolation with no adult supervision, who are very, very ill and they’re just lying on the ground on mats.”

Elora Mukherjee, another lawyer who visited the facility, told CBS News: “They were wearing the same dirty clothing they crossed the border with.

“It is degrading and inhumane and shouldn’t be happening in America.”

As stories of substandard conditions in facilities have continued to emerge, some volunteers have tried to donate supplies – only to be turned away by border officials.

One group told the Texas Tribune they spent $340 (£267) on nappies, wet wipes, soaps and toys for the Clint facility, but were ignored by all the agents on duty.

Another local resident who tried to visit the Clint station told the Tribune: “Knowing what’s happening in your community and that you can’t give these kids supplies to clean or clothe themselves – it’s heartbreaking.”

Texas Democratic state congressman Terry Canales later tweeted that Border Patrol also told his office “they do not accept donations”.

What have the authorities said?

In a statement, the border authority acknowledged that the Clint facility was not suited to the task.

“US Customs and Border Protection leverages our limited resources to provide the best care possible to those in our custody, especially children,” it said.

“As our leadership have noted numerous times, our short-term holding facilities were not designed to hold vulnerable populations, and we urgently need additional humanitarian funding to manage this crisis.”

The agency said it had moved children to more suitable facilities as soon as space was available.

On Monday, Democratic Representative Veronica Escobar, who had been deeply critical of the reported conditions, said she had been told that only 30 children remained in the Clint facility.

What are lawmakers doing?

Democrats in the House of Representatives have been trying to push through a $4.5bn bill in emergency aid for the border, but the issue has divided liberals, particularly those in the Hispanic and Progressive Caucuses.

Some lawmakers, including liberal Democrat Alexandria Ocasio-Cortez, say the additional funding could be used by the White House to continue raids and detentions.

“I will not fund another dime to allow ICE to continue its manipulative tactics,” Ms Alexandria Ocasio-Cortez said to US media.

Others, like Appropriations Committee chair Nita Lowey, said her fellow Democrats should not allow anger at President Donald Trump “to blind us to the horrific conditions at facilities along the border as the agencies run out of money”.

The most powerful elected Democrat, House Speaker Nancy Pelosi, met her rank-and-file members on Monday to discuss changes to the bill ahead of a Tuesday vote.

Democratic leaders said they would add language to the bill to ensure higher standards of medical care and nutrition for migrants in US custody.

They also want to set a three-month limit for any unaccompanied child migrant to spend at a shelter.

Some Democrats are opposed to the $155m in the bill that would go to the US Marshals Service, a law enforcement agency that detains migrants who illegally re-enter the country after deportation.

The White House has already threatened to veto the bill, saying it “does not provide adequate funding to meet the current crisis and… it contains partisan provisions designed to hamstring the Administration’s border enforcement efforts”.

Republicans are siding with the administration, opposing the migrant facility standards being pushed by the Democrats.

The Trump administration has requested more funding for Immigrations and Customs Enforcement (ICE) and the Departments of Defence and Homeland Security.

Where are the parents?

The separation of migrant children from their parents began in 2018 under a new “zero tolerance” policy from Mr Trump’s administration. It saw nearly 3,000 children separated before it was suspended.

Under the policy, announced in May 2018, those who crossed the border illegally were to be prosecuted – which required their children to be taken into care.

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Yet the US Government Accountability Office has reported that neither the Department of Homeland Security nor the Department of Health and Human Services were aware of the policy before it was publicly announced, and so were not prepared for the increase in children being detained.

There are also limits set by the US authorities on how many people can claim asylum each day, resulting in a waiting period that can last months.

Some migrants and their families are instead attempting dangerous crossings far from the official ports of entry, or relying on people smugglers to make the journey.

The number of migrants apprehended at the border surged in May to the highest level since 2006.

Seven migrants, including two babies and a toddler, were found dead in Texas this week by US Border Patrol. They are thought to have died from heat exposure.