A 16-year-old boy from Guatemala died Monday while in the custody of U.S. Customs and Border Protection, the agency said, becoming the fifth migrant child since December to die after being apprehended by immigration authorities. The child was found unresponsive during a welfare check at the Weslaco Border Patrol Station in South Texas on Monday morning, the agency said in a statement. He was apprehended for illegal entry on May 13 and taken to a processing center in the Rio Grande Valley before being transferred to the Weslaco facility Sunday, where he was awaiting placement with the Health and Human Services Office of Refugee Resettlement. The cause of the boy's death is unknown, CBP said.Earlier this month, another 16-year-old boy from Guatemala died while in government custody. Last week, a 2-year-old child died in the hospital after he and his mother were apprehended by Border Patrol in April. The toddler had been in the hospital for about a month before his death. The five children who have died after being apprehended by Border Patrol since December have been from Guatemala.