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THORNTON, Colo. (KDVR) — Police continue to search for a missing Thornton family. Detectives are searching for a toddler and her parents who were last seen on Monday.

The circumstances surrounding the family’s disappearance remain a mystery. The parents have two daughters. Police say they took the youngest daughter with them and left the 5-year-old behind.

Police have uncovered an illegal marijuana grow inside the family’s home on 130th Way in Thornton.

“That’s why it’s so perplexing. We don’t know, are they still local? Are they injured? Are they hurt? Did something bad happen to them – or did they just leave the state? We don’t know,” Thornton Police Department Officer Matt Barnes said.

We do know they left on their own. It was Monday morning when police say 48-year-old Zaiqiao Feng, 40-year-old Liu Nei Li and 2-year-old daughter, Anny Li, were last seen. They left in a gray 2008 Toyota Highlander with Colorado plates 231-REZ.

Neighbors said the family left in a “hurry” and tossed a duffel bag into the car. Police say the parents left their 5-year-old daughter at the house and told her they were going to the grocery store. Luckily, a relative who lives across the street found her wandering in the yard around 9 p.m. Monday night.

“We were just lucky a relative lived in the area and saw the girl in the yard and took her in to safety. If she would have remained in the home overnight or for days without anyone finding her – it’s concerning,” Barnes said.

According to Barnes, Anny has an underlying medical condition that requires frequent medication and regular doctor visits.

Thornton police do not know whether the parents have that medication or when Anny last visited a doctor.

When Thornton police executed a search warrant at the home on Wednesday night, they uncovered the illegal marijuana grow. Neighbors told FOX31 that they saw agents pull dozens of plants and equipment onto the driveway.

The 5-year-old girl is safe and with relatives. Thornton police say they have received numerous tips on potential sightings, but still have not been able to locate the family.

Anyone with information is urged to contact TPD at: 720-977-5150.