Investigators with the Colorado Bureau of Investigation were back in Pueblo Monday.

They are digging on the west side of the city, as part of the investigation into the disappearance of Kelsie Schelling, who hasn't been seen since 2013.

According to our affiliate in Colorado Springs, Schelling's mother was at the scene.

Schelling, 21, was last seen on Feb. 4, 2013, one day after she sent her eight-week ultrasound to her boyfriend Donthe Lucas.

That night, at the request of Lucas, Schelling drove from Denver to Pueblo. She arrived at Walmart at around 11 p.m., and texted she was “tired of waiting” around an hour later. She was never heard from again.

Later that morning, reports say Lucas took out $400 from an ATM in Schelling’s car using her card. He was also filmed driving her car to the Walmart parking lot. Three days later, a hooded figure drove off in the car, which was ultimately found at a hospital.

Lucas remains a person of interest but has never been charged.

Pueblo Police confirmed Thursday morning they are searching the yard in the 5100 block of Manor Ridge Drive for evidence related to Schelling's disappearance.

In a photo, authorities were seen digging homes in the yard. What evidence they're looking for is unclear.

Court records show he was arrested on Feb. 15, 2013 and charged with theft under $500 and identity theft.

Police alleged Lucas committed both crimes on Feb. 5, 2013 -- just one day after Schelling was last seen.

Both charges have been dismissed.

Lucas was convicted of driving under the influence in 2014. He was sentenced to 12 months probation and 24 hours of community service.