Two other passengers, another man and his 13-year-old son, were later found on the American side of the river. Border Patrol agents found the body of the 10-month-old baby on Thursday and pronounced the boy dead, according to a Customs and Border Protection official. Agents were still searching for the three migrants who had not been recovered.

The chaotic episode highlights the rising death toll as migrants from Central America try to cross the border with Mexico to request asylum in the United States. Two detained migrant children from Guatemala died in December while in Border Patrol custody, and a 16-year-old boy from Guatemala died earlier this week in Texas after arriving at a shelter for unaccompanied children.

Raft crossings into Texas are a common form of transit into the United States, with the Rio Grande Valley sector being consistently the Border Patrol’s busiest. With springtime water levels relatively high, the water is fast-moving in the area near Del Rio, said an official with Customs and Border Protection, who spoke on the condition of anonymity because he was not authorized to discuss the raft accident. Rescues are common because many of those attempting to cross have little, if any, experience with swimming, the official said, and crossing the river at night, as this group had, is particular dangerous.

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The river is patrolled regularly by Border Patrol agents, but migrants attempting to cross are often advised by smugglers to do so in areas that are difficult for the agents to see because they are obscured by trees or other natural barriers — making an accident such as an overturned raft in those areas even more dangerous as it can go unobserved by the authorities.