Eight migrants died and 37 were rescued as they tried to cross the rain-swollen Rio Grande River into the United States near Eagle Pass, Texas, U.S. customs officials said on Friday.

Border patrol agents, along with local fire and police agencies, were searching for possible additional victims a day after the Thursday incident, said Customs and Border Protection spokesman Rick Pauza.

A total of 53 migrants were taken into custody by U.S. border patrol agents on Thursday, including the 37 rescued from the river, Pauza said. Mexican government authorities arrested 39 people.

The Rio Grande swelled in recent days due to unusually heavy rains that flooded the streets of Piedras Negras, Mexico.

Other groups of migrants also struggled on Thursday evening to cross the fierce currents of the river between Piedras Negras and Eagle Pass.

Several men from Venezuela were successful after at least an hour attempting to ford the river’s fast waters, shirtless, with few belongings and using a rope to help one another, yelling “Help! Help!“ once close to the U.S. shore.

One man from the group clung to a concrete column under the international bridge for minutes after his friends made it to shore, afraid to let go as the water rushed past until his companions returned to help.

Texas has been at the center of a fierce national debate over illegal immigration that will likely play a role in the November mid-term elections.

Federal and local officials are scrambling to locate close to a dozen unaccompanied migrant children, after Houston police raised concerns about their whereabouts, Reuters reported on Friday.

The deaths and missing children underscore the challenges for President Joe Biden's administration as it faces a record number of unaccompanied kids arriving at the southwest border.

(Reporting by Dan Whitcomb; Additional reporting by Daina Beth Solomon in Mexico City; Editing by William Mallard & Simon Cameron-Moore)