Border deaths in Texas could be a preview of the summer

Two babies, a toddler and a woman were found dead near the U.S.-Mexican border, overcome by the sweltering heat in a glimpse of what could lie ahead this summer as record numbers of migrant families try to get into the United States.

Authorities believe the four may have been dead for days before the bodies were discovered Sunday in the Rio Grande Valley. No details were released on the victims' relationship.

It was the latest grim discovery of migrants who died while trying to cross the perilous desert and the swollen Rio Grande.

A law enforcement official close to the investigation told The Associated Press the four were overcome by the heat after fording the river. The official was not authorized to discuss the matter publicly and spoke on condition of anonymity.

Migrant families have been coming over the border in unprecedented numbers in recent months, reaching a peak in May, when 84,000 adults and children traveling together were apprehended. Nearly 500,000 immigrants have been detained at the border since the start of the year, resulting in dangerous overcrowding in U.S. holding centers.

A total of 283 migrant deaths were recorded along the 2,000-mile border last year. The death toll so far this year was not immediately released.