TUCSON, Ariz. — A medical examiner says two soldiers helping secure the Mexico border in Arizona died by suicide.

Pima County Chief Medical Examiner Dr. Greg Hess said Thursday the soldiers died of self-inflicted gunshot wounds.

Officials say 20-year-old Pfc. Steven Hodges of Menifee, California, died June 1 near Nogales, and 21-year-old Pfc. Kevin Christian of Haslet, Texas, died Sunday in Ajo, about 200 miles (320 kilometers) from Nogales.

Both soldiers were assigned to the Southwest Border Support Mission.

Military officials say the circumstances of the deaths are under investigation.

About 2,400 service members are assigned to the border mission.

The soldiers took their own lives as more are headed to the border.

Texas Republican Gov. Greg Abbott announced on June 21 that he will send another 1,000 National Guard troops to the U.S.-Mexico border while accusing Congress of failing to take action on the growing humanitarian crisis.

The governor said at an afternoon press conference among Republican leaders and Maj. Gen. Tracy Norris that additional Guard members will assist at new detention facilities in the Rio Grande Valley and El Paso and at ports of entry.

There are also 1,400 active-duty soldiers who remain on the border, according to an Army spokesman.

“My message to them is Congress is a group of reprobates for not addressing a crisis on our border and we’re not going to stand idly by and endanger the lives and safety of the state of Texas because Congress is refusing to do its job,” Abbott said.

Tensions along the border have been high.

A Marine fired his weapon while on duty along the U.S.-Mexico border in California and reported afterward that he had been attacked inside his vehicle by three people, officials said May 31.

John Cornelio, a spokesman for U.S. Northern Command, which oversees the military’s mission on the border, said the matter is under investigation. He confirmed that the Marine discharged his weapon but said he could not provide details until the investigation is completed.