People found dead inside a trailer truck in San Antonio

Half of the people found dead in trailer in San Antonio believed to be from Mexico, according to officials

More than a day after the discovery of 51 dead migrants in a stifling trailer in San Antonio, few identities of the victims have been made public, illustrating the challenges authorities face in tracing people who cross borders clandestinely.

By Tuesday afternoon, medical examiners had potentially identified 34 of the victims, said Bexar County Commissioner Rebeca Clay-Flores, who represents the district where the truck was abandoned. Those identities were not yet confirmed pending additional steps, such as fingerprints, and she described it as a challenge with no timeline on when the process might be finished.

READ MORE: How U.S. immigration policy is pushing migrants to take more dangerous routes

Among the dead, 27 are believed to be of Mexican origin based on documents they were carrying, according to Rubén Minutti, the Mexico consul general in San Antonio.

He said that several survivors were in critical condition with injuries such as brain damage and internal bleeding. He also said that about 30 people had reached out to the Mexican Consulate looking for loved ones.