Top House Democrats, preparing to take control of key committees early next year, have called for the preservation of all evidence related to the two child deaths in Customs and Border Protection custody.

An 8-year-old Guatemalan boy died Monday at a New Mexico hospital after suffering coughing, vomiting and fever, authorities said. It was the second such death this month.

The incoming committee chairs said in a statement that "our Committees in the House of Representatives will hold hearings and conduct oversight of the two deaths that occurred earlier this month, as well as the conditions under which thousands of children are being held ..."

They said the evidence includes "medical records, logs of health and welfare checks, and surveillance videos" at the holding facilities and processing centers.