(CNN) Jakelin Caal Maquin jumped up and down when her father told her they're leaving their impoverished Guatemalan village for the United States. When the rest of her family sent them off, nobody imagined the 7-year-old girl would not come back alive.

She died last week after Border Patrol agents detained her and her father in the New Mexico desert. Her death, which was only made public Thursday, has raised questions from members of Congress and advocates about how migrants are treated at the border.

The department's Inspector General's office is investigating the death and said its findings will be released publicly.

As the rest of her family mourns her 2,000 miles away, her father, Nery Gilberto Caal, 29, is at a shelter for migrants in El Paso, Texas.

Girl lived in extreme poverty, family says

Jakelin's mother Claudia Maquin (center) stayed in Guatemala caring for her three other children.

A makeshift white heart with Jakelin's full name across it stands in front of her family's home in the remote Mayan Q'eqchi' community of Raxruhá in the Alta Verapaz region.

"It really hurts," Domingo Caal, the girl's grandfather, told CNN en Español. "Honestly, it's hard to take in."

Domingo Caal says her granddaughter was happy to go travel to the US.

Jakelin was the second-born child of four children, raging from 8 years to 6 months. She was happy and healthy despite the family's financial struggles. Caal says Jakelin's father decided to leave because he was frustrated of living in extreme poverty.

"He wanted to work, because he said he could make a better living there," Caal said.

Speaking on behalf of Jakelin's mother, who only speaks a Mayan dialect, Caal said she hopes her husband stays in the US to work. The family is worried they would not be able to pay the debt they acquired to send Jakelin and her father north, he says.

She spent her birthday on the road

Jakelin and her father traveled for at least a week and spent her birthday on the road, her family says.

When they reached the New Mexico desert on December 6, they were among a group of 163 migrants who were detained by Border Patrol agents about half a mile west of the Antelope Wells port of entry, the CBP said. The immigrants included about 50 unaccompanied minors.

Four agents interviewed the group and looked for any signs of distress to determine whether medical care was needed. In that initial screening, officials said, there were no health issues.

Jakelin's father also claimed the girl was healthy on a government form.

"Our agents are almost always outnumbered in the middle of the night," a CBP official told reporters on a conference call Friday. "There is no indication that it was a lack of attention that resulted in this. The questions were asked. The observations were made and there was no indication that she had any health conditions."

The girl and her father were held at the port of entry in a facility with access to food, water and restrooms, CBP says, as they waited to be taken on the only bus available to the closest Border Patrol station -- about 95 miles away in Lordsburg, New Mexico.

The unaccompanied minors were the first to be transported.

Nearly eight hours after they were detained, Jakelin and her father were loaded on the bus.

Before leaving, her father told agents his daughter was sick and vomiting, the CBP said. An agent notified the station that the child would need emergency medical care.

When the bus arrived at the Lordsburg station about 6:30 a.m., the father told agents the child was not breathing, according to CBP.

A Border Patrol EMT "revived the child twice," the agency said. She had a temperature of 105.7 degrees. Local EMTs also provided care before she was transported at 7:45 a.m. by air ambulance to Providence Children's Hospital in El Paso, Texas.

"The reality of that part of the border is there's no faster way to get her to treatment than the one she was on," the CBP official said Friday.

Her father told officials that she had not been able to eat or drink water for days, according to DHS, but it's unclear when that interaction took place.

Results of autopsy are pending

At 11 a.m. on December 7, officials at the Lordsburg station were notified the girl had again been revived after going into cardiac arrest, the CBP said. A CT scan revealed brain swelling. She was breathing by machine and diagnosed with liver failure.

Jakelin died at 12:35 a.m. Saturday, the CBP said. Her father was there.

"Border Patrol Agents, including trained Emergency Medical Technicians did everything in their power to provide emergency medical assistance for Jakelin Caal Maquin immediately after her father notified the agents of her distress," CBP Commissioner Kevin McAleenan said in a statement.

CBP said it did not issue a statement about the child's death "out of respect to the family of the deceased." The agency is "currently reviewing its public disclosure and notification policy related to deaths in our custody."

The initial indication from the Providence Hospital is that she passed as a result of sepsis shock. The El Paso County medical examiner has not determined the cause or manner of death, and the case is pending further studies, according to a spokeswoman.

'Worst possible outcome'

In a statement, Cynthia Pompa, advocacy manager for the ACLU Border Rights Center, called for "a rigorous investigation into how this tragedy happened and serious reforms to prevent future deaths."

The girl's death comes months after a toddler died six weeks after being released from an Immigrations and Customs Enforcement facility in Dilley, Texas. The toddler's mother and her attorneys alleged she contracted a respiratory infection after they arrived at the detention center and that ICE provided substandard medical care for the 19-month-old.

The child and her mother came from Guatemala and were detained after crossing into the United States via the Rio Grande.