YUMA, ARIZ. >> More thorough initial health screenings for migrants, as well as secondary screenings, will be held for every child in Border Patrol custody following the deaths of two Guatemalan children this month, according to the Department of Homeland Security.

Homeland Security Secretary Kirstjen Nielsen was visiting Yuma, Arizona, today, a day after her trip to meet border officials and medical staff in El Paso, Texas.

“The system is clearly overwhelmed and we must work together to address this humanitarian crisis and protect vulnerable populations,” Nielsen said in a statement. She called on Congress to “act with urgency.”

Late Friday, El Paso Mayor Dee Margo said he was among those who met with Nielsen, saying they discussed “our immigration needs on the border.” The statement from Margo, a Republican, did not mention the deaths of migrant children or whether it was discussed.

The trip came days after the death of 8-year-old Felipe Gomez Alonzo in Alamogordo, New Mexico. Felipe was the second Guatemalan child to die in government custody in three weeks. A 7-year-old girl died in El Paso earlier this month.

Nielsen has called the death “deeply concerning and heartbreaking” and requested medical help from other government agencies, including the U.S. Coast Guard. As Nielsen made the trip to Texas, New Mexico’s Democratic senators, Tom Udall and Martin Heinrich, sent her a letter Friday seeking answers about the boy’s death.

“The timeline, action and factors that led to Felipe’s death are still developing, but the information that has become public so far is alarming and demands immediate attention and investigation,” the letter says.

President Donald Trump blamed Democrats for migrant deaths at the border Saturday. He tweeted the deaths are the fault of “their pathetic immigration policies that allow people to make the long trek thinking they can enter our country illegally.”

He went on to say “The two children in question were very sick before they were given over to Border Patrol.”

U.S. Rep. Raul Grijalva, an Arizona Democrat whose district includes Yuma and much of the U.S.-Mexico-border, on Saturday issued a statement saying Nielsen was visiting Yuma “under the dark cloud of a Republican-induced government shutdown, the president’s threats to close the border and the tragic deaths of two children in DHS custody.

Felipe and his father, Agustin Gomez, were apprehended by border agents on Dec. 18 near the Paso del Norte bridge connecting El Paso to Juarez, Mexico, according to U.S. Customs and Border Protection. The two were detained at the bridge’s processing center and then the Border Patrol station in El Paso, until being taken at about 1 a.m. Sunday to a facility in Alamogordo, New Mexico, about 90 miles (145 kilometers) away.

After an agent noticed Felipe coughing, father and son were taken to an Alamogordo hospital, where Felipe was diagnosed with a common cold and found to have a fever of 103 degrees Fahrenheit (39.4 degrees Celsius), CBP has said.

Felipe was held for observation for 90 minutes, according to CBP, before being released with prescriptions for amoxicillin and ibuprofen.

But the boy fell sick hours later on Monday and was re-admitted to the hospital. He died just before midnight.

New Mexico authorities said late Thursday that an autopsy showed Felipe had the flu, but more tests need to be done before a cause of death can be determined.