The deaths of a woman and her 15-month-old son who were struck by a commuter train in Monrovia Wednesday morning were being investigated as a murder-suicide, authorities said Thursday.

Therese Papagayo, 36, of Monrovia, and her 15-month-old son were struck and killed by an L.A. Metro train about 8:45 a.m. at the California Avenue crossing, just north of Duarte Road, according to Los Angeles County Department of Medical Examiner and Monrovia Police Department officials.

An autopsy determined Papagayo died from “blunt force traumatic injuries,” and the death was ruled a suicide, according to coroner’s records. The child’s identity had not been released by coroner’s officials Thursday.

Detectives were investigating the case as a murder-suicide, Monrovia Police Department Lt. Jaime Alfaro said.

No one was injured aboard the Metro “L” Line train, Los Angeles County sheriff’s officials said.

The Sheriff’s Transit Services Bureau, along with Arcadia Police Department, were assisting Monrovia police in the investigation.