RIO GRANDE CITY – Investigators looking into a decades-old cold murder case in Starr County are speaking out.

On Thursday, DPS Investigators announced they increased the reward for information leading to an arrest in the murder of 22-year-old Laura Guadalupe Guerra.

Starr County Sheriff’s Office and the Texas Rangers are preparing to interview a person they suspect is a witness in the case.

Guerra was found shot to death in a wooded area across the street from the Rio Motel in Rio Grande City. It happened in May of 1990.

Investigators believe she may have been killed at the hotel and her killer later dumped her body.

They said even minor details could lead to a break in the case.

“I would really value somebody that could tell me the last hours of Laura’s life here on Earth,” Starr County Sheriff’s Lt. Erasmo Rios said.

“They knew who she was hanging out with, they knew where she was at the time of the murder, who she might have been traveling with or what she might have been doing. Those are all key things,” Reid Rackley with the Texas Rangers said.

Authorities believe that a possible witness – known in the area back in the 90’s as “Gaston Garza” or “Mariano” – may have information they need.

Anyone with information about the murder can call 1-800-252-8477.