The bodies were handed over to Tania Avalos in Mexico on Wednesday, who is Martinez's wife and the child's mother. They left Matamoros, Mexico, on Thursday.
Her bodies are driven to Monterrey, Nuevo Leon state, which is about a four-hour drive away. According to the Salvadoran Ministry of Foreign Affairs, the bodies are flown from Monterrey on a commercial flight to San Salvador, El Salvador.
It is not clear if the flight will start on Thursday evening or Friday morning.
The family calls on the authorities to ensure their privacy on the journey.
Funeral arrangements have already been made.