An Oregon woman whose unborn son was cut from her body died following a struggle with her killer, according to court documents.

Heather Snively, 21, had bite marks on the back of her elbow and her alleged attacker, Korena Roberts, had a five-inch scratch on the left side of her neck and visible injuries on her arms, Washington County Sheriff's Detective Murray Rau wrote in a search warrant affidavit released Monday.

"The scene of this crime was very bloody, and, based on my own observations of the physical evidence, was the scene a violent struggle involving the suspect and the victim," Rau wrote.

Roberts, 27, has pleaded not guilty to aggravated murder and other charges in the death of Snively, found dead June 5 in the crawl space at the house Roberts and her boyfriend rented west of Portland.

Investigators believe Snively, who had recently moved to the state from Maryland, met Roberts through an online classified service, where both were looking for baby clothes.

The documents released by a Washington County judge listed what police seized during the investigation, such as computers, a steak knife, CDs of Agatha Christie mysteries and numerous items suspected of having blood on them.

The affidavits also include an account from Yan Shubin, Roberts' boyfriend of the past five years, of Roberts' false claims of pregnancy in the months leading up to the bizarre day the killing took place.

Shubin, who is not facing charges, said Roberts told him in November she was pregnant and dealing with morning sickness. Claiming to be pregnant with twins, Roberts started gaining weight, taking prenatal vitamins and attending midwife classes at a community college. Shubin said Roberts reported making trips to a doctor, but when the pair went for an ultrasound appointment, it turned out nothing had been scheduled.

Shubin said he got to work at 6 a.m. on June 5 and returned home for lunch about five hours later. Roberts made him a sandwich; everything seemed normal.

At 2:30 p.m., he told detectives, he left work and received an urgent call while at a bank.

According to Shubin, Roberts said "I need you" and sounded like she was in pain.

When Shubin arrived home, he saw blood on the floor and headed to the bathroom. The water was running while Roberts, wearing only a bra, sat in the tub with the lifeless infant.

Shubin took the baby and started CPR. Paramedics arrived and brought Roberts and the child to the hospital, where doctors quickly determined the baby was dead and Roberts had not just given birth.

Roberts claimed the baby had a twin, the documents state, and Shubin told authorities there was possibly another baby at the house. That led police to return.

Officers found much blood, but no baby. While inside, a sergeant got a call from the hospital, where Shubin had spent a brief time alone with Roberts.

"According to Yan, Korena told him that she did a horrible thing," the documents state.

Shubin told police about the crawl space in which Snively's body was later found by the sergeant.

"[The sergeant] told me that the body was very ashen, and he could see that the abdomen was sliced open," Rau wrote.

Prosecutors have not said how Snively was killed, other than autopsy results which showed blunt force trauma. It has also not been said which type of tool was used to cut Snively's abdomen. Shubin told investigators he buys razor blades for his work, and a pack he bought went missing two days before Snively's death, the documents state.

The authorities have yet to release a motive for why they think Roberts would fake a pregnancy and try to steal a baby. Shubin told a detective that Roberts, who has two children from prior relationships, informed hospital staff that she had been on antidepressants since her last pregnancy.