Central American migrants, traveling in a caravan, hold a demonstration following the death of 7-year old Jakelin Caal, who died two days after being taken into custody by border patrol agents in a remote stretch of New Mexico desert, outside a temporary shelter downtown Tijuana, Baja California state, Mexico on Dec. 15, 2018. (Xinhua/AFP)

WASHINGTON, Dec. 20 (Xinhua) -- U.S. Secretary of Homeland Security Kirstjen Nielsen will answer questions Thursday from lawmakers in the House Judiciary Committee about the recent death of an immigrant girl who died after being held in custody at a U.S. Border Patrol station on the southern border.

The girl, 7-year-old Jackelin Caal from the Central American country of Guatemala, died on Dec. 8, less than two days after being detained separately from her father at southern New Mexico as the pair crossed the border into the United States.

The Department of Homeland Security (DHS) said in a statement on Friday that Caal died from dehydration and septic shock after having gone days without food and water.

Nielsen's testimony came as the Democratic Party is set to take control of the House when the new Congress convenes on Jan. 3. The Democrats view the immigration policies of the administration of President Donald Trump as a priority of their oversight effort.

Apart from Thursday's hearing, the House Judiciary Committee and the Homeland Security Committee, both of which will be headed by Democrats from January onward, notified Nielsen in a joint letter Friday that they would intensify scrutiny over the DSH's role in the Caal case.

"Please be assured that our committees will be conducting further oversight of your efforts on this important matter in the upcoming year," the letter read, according to a report by The Wall Street Journal.

More broadly, the WSJ said, Democratic oversight on the White House's immigration policies will also involve probes into other Cabinet-level departments, such as the Department of Justice and the Department of Health and Human Services.

Trump in a tweet on Wednesday praised border agents and the troops he deployed on the border for their "great job," thanks to which he said the Caravan migrants "didn't get through and none are forming or on their way."

"Border is tight," Trump claimed, while recent data from the U.S. Customs and Border Protection (CBP) revealed a different reality: The CBP arrested or denied entry of 62,456 border-crossers on the southwest border in November, up from 60,772 apprehensions or inadmissibles registered in October.