A 45-year-old undocumented immigrant from Mexico died in Border Patrol custody Monday after crossing the U.S.-Mexico border into Texas, marking the third person to die in the agency's custody since December.

The immigrant illegally crossed the border and was arrested by the Roma (Texas) Police Department on Feb. 2, requested medical attention and was taken to a local hospital, according to a statement released Monday night by Customs and Border Protection. The immigrant "was cleared" by officials at the Mission Regional Medical Center and was handed over to Border Patrol officials at the Rio Grande City Border Patrol Station, according to the CBP statement.

The following day, after receiving a welfare check by CBP officials, the immigrant again requested medical attention and was taken to the McAllen Medical Center, where the immigrant was diagnosed with cirrhosis of the liver and congestive heart failure, CBP said. The immigrant remained at the hospital before dying on Monday morning.

The incident follows two cases in December when children from Guatemala, ages 8 and 7, died after crossing the U.S. border into New Mexico, drawing widespread condemnation from critics of the Border Patrol.

That prompted Customs and Border Protection Commissioner Kevin McAleenan to issue new guidelines requiring his agents to more quickly inform CBP leadership, Congress, and the public of the death of people in its custody. Department of Homeland Security Secretary Kirstjen Nielsen later followed up by ordering more robust medical screenings of children it holds in its custody.

Those deaths followed intense criticism of the agency's handling of children during the administration's now-rescinded "zero-tolerance" that led to more than 2,800 family separations along the border.

Customs and Border Protection spokesman Andrew Meehan said the official cause of death in Monday's case remains unknown, and that the immigrant's identity is not being released. Meehan said the department is following newly created notification guidelines following deaths in its custody and has alerted Congress and the Mexican government of the immigrant's death.

"This loss of life is tragic," Meehan said in a statement. "Our condolences go out to the family and loved ones. CBP remains committed to ensuring the safe and humane treatment of those within the care of our custody."

Border Patrol officials have said they cannot handle the influx of family units and unaccompanied minors who have flooded the southwest border in recent years, many of them requesting asylum in the U.S.

In the past four months, a monthly average of 24,975 members of family units and 5,031 unaccompanied minors have crossed the southern border, according to CBP data. The family unit average is far higher than the monthly average of 6,406 over the same period ending in 2018.

That surge has led the Trump administration to try and limit the number of people who can request asylum, actions that have been blocked by the federal courts. The surge also contributed to President Donald Trump's decision on Friday to declare a national emergency to expand the southern border wall, which will also lead to a flood of lawsuits.

The new Democratic-led House of Representatives has vowed to investigate housing conditions for migrants along the border. Part of the budget deal that averted a government shutdown last week included $415 million for humanitarian relief "specifically for medical care" and to improve Border Patrol processing facilities in the region.

CBP's summary of Monday's death did not indicate whether the immigrant was requesting asylum. It noted that the immigrant was caught by police in a second attempt to illegally enter the U.S.