A Utah couple and their three children found dead in their home last month were likely poisoned, their bodies found together in a locked room with cups next to each of them, and empty bottles of methadone and nighttime cold medicine in a trash can.

Police in Springville aren't saying who killed the family or whether one of the parents might have been involved.

Toxicology results have not determined an exact cause of death, but search warrants obtained Wednesday say the family was likely poisoned.

Benjamin and Kristi Strack were in bed, with children ages 11 through 14 lying around them, tucked in bedding up to their necks, according to the search warrants. Kristi Strack had a red liquid coming out of her mouth.

Some of the bodies looked to have been positioned after they died Sept. 27. They were found by the couple's older son and Kristi Strack's mother, who said she couldn't believe "she" would do this to the kids but wouldn't elaborate, police wrote.

Investigators found empty methadone bottles, 10 empty boxes of nighttime cold medicine and two boxes of allergy medicine in their garbage, along with a red liquid substance in Pepsi cups. They also found a pitcher of red juice, a purple bucket with yellow liquid, a bag of marijuana and other medications, including sleeping pills.

Springville police Lt. Dave Caron said Wednesday he couldn't comment on the search warrant or speculate about the cause of death until results of a toxicology test come back. That's expected in late November, he said.

"Until I get those, I really don't have anything," he said. "I could come up with all sorts of theories, but it's not helpful."

The search warrant says it wasn't normal for the children to be in their parents' room because they have their own rooms.

Kristi Strack was last seen alive at 6 a.m. by the older son's girlfriend, who also lives in the home. The girlfriend went back to sleep after talking with Kristi Strack, and the house was quiet when the older son and his girlfriend left the house that afternoon.

When they returned at 7 p.m. and saw the house was still quiet even though all the cars were in the driveway, they knocked on the master bedroom door. When no one answered, the couple called Kristi Strack's mother and her friend, who helped them force it open.

Authorities have previously said the five did not die violently.

The five were identified as Benjamin Strack, 37, his wife, Kristi, 36, and three of their children: Benson, 14, Emery, 12, and Zion, 11.

Little is known about the family. A family spokesman has declined to reveal much and, at a vigil, family members declined comment.

Benjamin Strack's former boss said he worked off-and-on for six to seven years at AK Masonry, a bricklaying company, and had borrowed money in the past. Court records show Benjamin and Kristi Strack pleaded guilty to misdemeanor forgery charges in 2008 and disorderly conduct the following year.

Springville is a city of about 30,000 near Provo, about 45 miles south of Salt Lake City.