"She works in a small convenience store right near her home. Around midnight she locked up as per normal and left the store and was never seen again," said Conroe Police Sgt. Joe Smart.
Martha never returned to her family's mobile home just across the street. Her 18-year-old daughter reported her missing the next day.
Martha's husband, Luis Hernandez Jimenez, 54, is charged with tampering with evidence by giving a false statement. According to detectives, he said she had "just left" and appeared distraught.
"It was reported and the investigation led us to believe that she left on her own," Sgt. Smart said. "Then evidence surfaced later in the week that led us out (to the landfill)."
Police say new information developed which led them to believe Martha may have met with foul play. That information has not been disclosed.
An unauthorized entry was made into the Security Landfill early Sunday morning. Police are operating on the possibility that it could have been Luis Jimenez, who is an employee of the landfill.
Police have been searching the landfill since Monday. A number of officers were on the scene this morning, searching with rakes and shovels as a backhoe moved larger piles of trash.
Texas Equusearch is also assisting in the search. Founder Tim Miller calls conditions "difficult, but noy as bad as Aruba," where he searched for missing US teenager Natalee Holloway.
Cadaver dogs can't be used, Miller says, because they alert to medical waste in the landfill. More than 10acres of the landfill are being examined, layer by layer.
Sgt. Smart said, "We've been as fortunate as you can be on something on like this, with the fact that only a few days have passed and this particular landfill is very methodical in the way that they grid and the way they dump and cover their garbage. We've been able to work with the management here and they've been able to show us exactly what would have been exposed area around Sunday."
Sgt. Smart added that he believes Martha will be found in the landfill where crews have been searching. The search continues on Thursday.
Jimenez is in Montgomery County Jail on $50,000 bond. He was arrested on Sunday. A Conroe Police Department investigation is ongoing.