The death of a 15-year-old girl discovered this week in a vacant Cape May County house has been ruled a homicide.

Detectives found the body of Nicole Angstadt inside the crawl space of a property at 100 Vermont Ave. in Middle Township, according to a statement from the county Prosecutor's Office. Her mother had reported her missing Dec. 1, and investigators were probing her disappearance when they searched the home.

An autopsy conducted Tuesday confirmed Angstadt's identity and revealed that she was killed, prosecutors said. Authorities declined to elaborate on the cause of her death due to the ongoing nature of the investigation, but said they did not believe the killing of the Lower Township teenager was a random act.

The investigation has resulted in three arrests, all on charges unrelated to Angstadt's death, prosecutors said.

Charles Mosley, 32, was taken into custody Monday after authorities learned he allegedly had a sexual relationship with Angstadt. Mosley, of Rio Grande, N.J., was charged with sexual assault of a person at least 13 but less than 16, endangering the welfare of a minor, and trespassing. He was being held at the Cape May County Jail after failing to post $250,000 bail.

Also on Monday, authorities charged LaQuan Harris, 20, and Derrick Powers, 23, both of Rio Grande, in connection with two separate armed robberies. The pair allegedly robbed nine juveniles at Mulligan Park in Lower Township on Dec. 5 and struck a victim with a handgun during a robbery in Middle Township on Dec. 8.

Both were charged with two counts each of first-degree armed robbery and second-degree conspiracy to commit armed robbery and were lodged in the Cape May County Jail in lieu of $200,000 bail.

It was not clear how Harris and Powers were connected to the investigation into Angstadt's death.

Anyone with information was being asked to contact the Prosecutor's Office at 609-465-1135.

215-854-2305; awigglesworth@philly.com