The Venezuelan Attorney General office on Monday announced an investigation into allegations of torture of migrants sent to an El Salvador prison from the US.

The more than 250 Venezuelans were returned home on Friday in a prisoner exchange with the US. They had been detained in the notorious Terrorisom Confinement Center, or CECOT, prison in El Salvador since March.

What are the torture allegations?

At a press conference on Monday, Venezuelan Attorney General Tarek Saab showed videos of former detainees describing human rights abuses and showing injuries.

Saab said prisoners suffered several kinds of mistreatment, including sexual abuse, beatings, denial of medical care or treatment without anesthesia, and that they were given rotten food.

He said that his office will investigate El Salvador's President Nayib Bukele, Justice Minister Gustavo Villatoro and Head of Prisons Osiris Luna Meza for the alleged mistreatment and human rights abuses of the Venezuelans. 

Andry Hernandez Romero, a 32-year-old beautician among those sent to the prison, described the abuses in a video presented by Saab.

"We were going through torture, physical aggressions, psychological aggressions," he said "I was sexually abused."

Many spoke of being held in inhumane cells, deprived of sunlight and ventilation. They had no access to lawyers or relatives.

The Venezuelan governement has said the group will be medically assessed, interviewed, and issued new Venezuelan ID cards before being returned home.

Bukele's office has not yet responded to the abuse allegations.

Why were the Venezuelan migrants sent to El Salvador?

The Venezuelan migrants spent months detained in the maximum-security prison after being deported by the US. They had been sent to the CECOT prison after U.S. President Donald Trump invoked the 1798 Alien Enemies Act to deport alleged members of the Tren de Aragua gang. This rarely used wartime law led to deportations without court hearings and resulted in an international outcry. Many family members and lawyers of the accused denied any gang ties.

They were released on Friday in exchange for 10 US nationals jailed in Venezuela.

Reaction to the prisoner release 

The opposition coalition in Venezuela has celebrated the release of the prisoners, but said on Sunday that nearly 1,000 people remain jailed in Venezuela for political reasons, with 12 arrested in recent days.

Venezuela itself faces an investigation by the International Criminal Court in The Hague.

Mercedes Yamarte, mother of one of the men released on Friday, told French news agency AFP that she was preparing a welcome party for her 29-year-old son Mervin. On Monday, she received a call and heard "Mom, it's Mervin."

"I hadn't heard my son's voice in four months and seven days, listening to him was a joy, a joy I cannot describe," she said.

Edited by: Elizabeth Schumacher