COTULLA, Texas -- A woman who was eight months pregnant was strangled and found in a run-down cemetery, authorities said.

The killing happened Tuesday night in Cotulla, about 85 miles south of San Antonio.

Investigators and family members said the victim is Valerie Benavides, 26.

Benavides, a resident of Cotulla, had witnessed a robbery in town, according to her relatives.

They said she was going to authorities with names of people she thought were involved in the robbery.

The next day her body was discovered by someone visiting Cristo Rey Cemetery, a mile outside Cotulla.

"They happened to be going by the Cristo Rey Cemetery and saw a bundle," La Salle County Sheriff Robbie Wood said. "They got closer and saw that it was a body. My deputies went out there and they verified that it was a human body."

The Texas Rangers are helping investigate the killing. There is no one in custody, but authorities said they are interviewing five "persons of interest."