(CNN) -- Homicide police in San Diego, California, are investigating Monday's death of a Mexican man who was beaten and tasered by U.S. border agents three days earlier, officials said.
The Mexican government says it wants an explanation about what happened to Anastasio Hernandez Rojas while he was in U.S. custody.
"The Foreign Ministry expresses its indignation and reiterates its most energetic condemnation of the events that led to the death of Mr. Hernandez Rojas," the agency said in a release. "The Mexican government has proceeded to ask U.S. authorities for an exhaustive investigation of these events and will closely follow its developments."
The altercation occurred Friday night at the San Ysidro Port of Entry when U.S Customs and Border Protection agents were trying to deport Hernandez to Mexico, San Diego and federal authorities said. Hernandez became combative, the officials said, and force was used to restrain him.
"One of the agents used a baton to administer to the subject to get him to stop fighting," said San Diego homicide Capt. Jim Collins. "When that was not successful, they used the Taser."
Hernandez stopped breathing shortly after being tasered, San Diego police said in a statement Saturday.
Notimex, the Mexican government-run news agency, said the man was brain dead and doctors proposed disconnecting him from life-support.
He died Monday afternoon at Sharp Chula Vista Medical Center in Chula Vista, California, a hospital spokeswoman and police said. Neither the hospital nor police would give a cause of death. A medical examiner will perform an autopsy Tuesday or Wednesday, Collins told CNN.
The police investigation will take three to four weeks, and a report will be submitted to the U.S. attorney's office, Collins said. San Diego police routinely investigate any deaths involving local or federal officials in the department's jurisdiction, the homicide captain said.
The man's death has drawn great attention in Mexico, where newspapers and other media widely reported the border incident and his death.
The Mexican National Commission on Human Rights issued a statement Sunday in which it "condemned the aggression" against the man.
"We consider it necessary and urgent that diplomatic authorities from our country intervene in defense of our compatriot's rights," the statement said.
The commission is an autonomous body that is part of the Mexican government.
U.S. Border Patrol agents detained Hernandez and his brother Friday evening for entering the United States illegally, police said.
The men were transported to the San Ysidro Border Patrol station, where Hernandez signed a voluntary return order, San Diego police said. When he was taken to the border to be handed over to Mexican officials, Hernandez became violent when the agents removed his handcuffs, police said.
"The agents and the subject all fell to the ground during the fight and the agents radioed for assistance," the police statement said. "Customs and Border Protection agents came to the assistance of the Border Patrol agents and also struggled with the subject. Due to the combative behavior of the subject, an agent from Customs and Border Protection used a Taser to subdue him."
Agents administered CPR and called from paramedics when Hernandez quit breathing, police said.
Lloyd Easterling, director of media relations for U.S. Customs and Border Protection, offered the same version of events in an e-mail Tuesday to CNN.
"After repeated orders to cease, one of the officers deployed a taser to subdue the individual and maintain officer safety," Easterling wrote.
He did not mention use of a baton.
Hernandez's age was unclear Tuesday. San Diego police say he was 32. Notimex, the Mexican government's news outlet, gave his age as 42.
He was the father of five children, including 4-year-old twins, and had lived in San Diego for 27 years, Notimex said. U.S. officials said he was in the country illegally.
Notimex reported that Hernandez's brother, Pedro Pablo, said a U.S. agent kicked him in the chest while they sat handcuffed on the floor. Pedro Pablo said his brother came to his defense and from that moment on the agents were hostile to the two men, the news agency reported.