A Chicago nonprofit organization that runs a facility holding immigrant children separated from their parents at the U.S.-Mexico border said it's investigating allegations some children made after leaving the facility and reuniting with their parents. The nonprofit, Heartland Alliance, called the allegations "disturbing" and said it launched an investigation over the weekend, when the Washington Post published interviews with children who were housed at Heartland's Casa Guadalupe facility.

Two boys from Brazil, 10-year-old Diego Magalhaes and 9-year-old Diogo De Olivera Filho, told the Post that a 5-year-old boy who tended to throw fits in class was injected with something that put him to sleep.

"I was very scared," Diego told the newspaper. "I thought they were going to inject me too."

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Heartland Alliance said in a statement that "injections for behavior management" aren't part of the facility's practices.

"Ensuring the safety and well-being of children is our top priority," the statement said.

Sirley Silveira Paixao, an immigrant from Brazil seeking asylum in the U.S., looks at her 10-year-old son Diego Magalhaes after Diego was released from immigration detention July 5, 2018, in Chicago. AP Photo/Charles Rex Arbogast

Diego also told the Post that he wasn't examined by a doctor or a nurse when he fell on a concrete basketball court and injured his arm. He said he had to wear a temporary cast for weeks.

"It still hurts," Diego said.

Diogo told the newspaper that he was threatened with being detained until he was an adult for sleeping in.

"They told me, 'If you keep doing that, you're going to have to stay here until you're 18,'" he said.

Lidia Karine Souza and her son Diogo De Olivera Filho smile at each other at the Mayer Brown law firm during a news conference shortly after Diogo was reunited with his mother June 28, 2018, in Chicago. AP Photo/Charles Rex Arbogast

An 11-year-old boy from Guatemala, Victor Veliz, also told the newspaper that there were consequences for not following the shelter's schedule: Two male workers "dragged" him inside after he dawdled on a soccer field.

Victor also said he needed permission to hug his 9-year-old sister, Leidy, who was being detained at the same facility.

"There were people there who only spoke English, and they always said to us, 'No touch, no touch,'" Leidy told the Post.

The siblings didn't get many chances to hug. They said they were housed in separate buildings and only saw each other during recess two times a day.

On Tuesday, Illinois' senior senator, Senate Democratic Whip Dick Durbin, asked the inspector general for the federal Department of Health and Human Services to look into the children's allegations about Casa Guadalupe.

The department oversees the facilities housing the separated children. Last month, the department's watchdog opened an investigation into the Trump administration's policy of separating children from their parents who have been accused of crossing the border illegally.

"Every effort must be made to ensure that, once in the care of HHS grantees like Heartland, these children are compassionately cared for—both physically and emotionally," Durbin wrote in a letter to David Sinski, an executive director and vice president at Heartland Alliance.

Department spokesman Mark Weber wouldn't comment to the Post on specific cases but said that "any allegation of abuse is taken seriously." Heartland said in its statement that it welcomed Durbin's call for the investigation.