A man suspected of killing his longtime partner and the mother of his children is accused of driving the victim’s body to Mexico.

Erick Alcantar Almanza, 44, was arrested in connection with the murder of Aracely Romero. Officials say Almanza smuggled the victim’s body across multiple U.S. border checkpoints between San Diego and Tijuana before his arrest on Sunday, according to Baja California prosecutor Miguel Angel Gaxiola.

The investigation began after a woman called Mexican authorities to report that her son had killed the mother of his five children. Detectives believe Almanza killed Romero in Long Beach then drove her body across the U.S.-Mexico border over the weekend.

“Looking at the records, this appears to be what we have; this could be the second or third similar case where someone crosses the border with a deceased person and tries to hide it in Tijuana,” Gaxiola said. “Right now, we are exchanging information to try to locate the scene of the crime that occurred there in Long Beach.”

According to the couple’s eldest son, the family last saw their mother on Friday. The son told NBC4 that Almanza called his children as he was driving and allegedly confessed to killing their mother.

The suspect struggled with mental health issues for years, according to the son. The couple shared five children whose ages were between 16 and 26.

Almanza told investigators he and Romero had an argument before the victim was killed, but a motive for the murder has not been disclosed. A cause of death for Romero was not revealed.

The investigation is ongoing.