The volunteer, who was also a federal employee, had a medical emergency Friday while at the facility and later died.
"That was the only reason that there were ambulances there the night before," Jackson Lee said.
The volunteer's death was due to underlying health conditions, according to Jackson Lee, but it wasn't clear what led to the episode. The volunteer was not identified.
RELATED: 500 migrant girls transported from Houston holding facility after reported incident
The incident happened prior to the facility's closure and the transfer this weekend of hundreds of migrant girls who were housed there.
Immigrant led organizations were still searching for answers behind the decision to close the location, more than two weeks after it opened.
Buses were seen leaving and arriving at the shelter, and boxes and computers were being moved by workers Saturday.
"Today, HHS announced that all of the children in HHS Office of Refugee Resettlement (ORR) care at the Emergency Intake Site (EIS) for Unaccompanied Children at the National Association of Christian Churches site in Houston, Texas (NACC Houston) will be immediately unified with sponsors or transferred to an appropriate ORR facility," U.S. Department of Health and Human Services officials said in a statement released Saturday.
Nearly 130 of the reported 450 girls at the site already have plans to be united with a sponsor, HHS officials said.
Representatives from local non-profit, FIEL Houston, said Saturday afternoon the conditions inside the facility were not appropriate for the girls being kept there.
FIEL executive director Ceaser Espinosa said the conditions inside the warehouse were 'inappropriate for anyone, especially young girls', who range in age from 13-17 years old. He added that employees of the facility would only let the teens get out of their cots a few times a day to shower and use the restroom. Congresswoman Jackson Lee said Saturday that she didn't see that happening when she visited.
"I saw unrestrained children," Jackson Lee said. "The children in some of the other facilities that have a large population, they always have the carts near each other. Technically they're six feet apart, but I saw unrestrained children to be able to move around and move around to get their food. I certainly did not spend a day there, but I didn't see unhappy children. I saw children who wanted to get as quickly as possible reunited with their families."
Something is happening at the Children Detention Center in Houston pic.twitter.com/6ohJEVb2Ws— FIEL Houston 🦋 (@FIELHouston) April 17, 2021
"The NACC Houston EIS and other Emergency Intake Sites are intended for use as a temporary measure," HHS officials said in Saturday's statement.
While the reason for the transfers Saturday weren't immediately clear, the agency cited "continuity of care under conditions that meet our strict standards of care in ORR state licensed shelters, the Carrizo Springs Influx Care Facility or Emergency Intake Sites where beds have become available."
The unaccompanied migrant children began arriving at the Houston location, which is not being disclosed for security reasons, on April 2, a day after it opened.
Federal authorities, community and faith leaders worked together to prepare the 500-bed shelter that was operated by the National Association of Christian Churches.
SEE ALSO: Congresswoman gives update on 300 migrant girls housed in Houston
Prior to the Houston closure, there were 10 migrant housing facilities total; nine are in Texas and one is in San Diego.
Here are the details for the remaining Texas centers:
- Carrizo Springs - 500 beds
- Carrizo Springs - 952 beds
- Fort Bliss - 5,000 beds
- Dallas - 2,300 beds
- Midland - 700 beds
- Pecos - 2,000 beds
- San Antonio - 2,400 beds
- San Antonio - 350 beds
RELATED: More than 4,000 migrants, many kids, crowded into Texas facility