The suspected driver of a truck where 53 migrants died from heat in Texas did not know that the air conditioner had stopped working, court documents say.
Homero Zamorano, 45, was found hiding near the truck on Monday, officials say. He is one of four people charged.
Mr Zamorano and alleged conspirator Christian Martínez, 28, are accused of sending text messages to each other before and after the truck was found.
It is the deadliest human trafficking incident in US history.
Several children found in the vehicle are still being treated in hospital. The victims were from Mexico, Honduras, El Salvador and Guatemala.