KEANSBURG-- Authorities in Monmouth County said Friday they have arrested and charged a man with the killing of an 11-year-old Keansburg girl.

Andreas Erazo, 18, has been charged in the girl's death, the Monmouth County Prosecutor's Office said. Erazo lives upstairs in the same apartment building as the victim, 11-year-old AbbieGail "Abbie" Smith.

He is expected to appear before Superior Court Judge Richard English on Friday afternoon for a detention hearing.

The Middlesex Regional Medical Examiner's Officer is expected to conduct an autopsy later Friday to determine AbbieGail's cause of death.

AbbieGail was found in a rear area of the Hancock Arms apartments, where she lived with her mother. The Monmouth County Prosecutor's Office said previously her death was being investigated as a homicide.

Abbiegail's mother first reported her missing Wednesday night. During the course of the search, the prosecutor's office was called in to assist.

Authorities said earlier Thursday that no member of her immediate family appeared to be involved in her death. Prosecutor Christopher J. Gramiccioni also sought to reassure the shaken community after Abbiegail's body was discovered.

"We have no reason to believe that you or your child should be worried," Gramiccioni said to a parent during a news conference, describing Abbiegail's killing as "an isolated crime."

In a statement, John Niesz, superintendent of the Keansburg school district, said the community has "suffered a tragic loss." The school district will provide grief counselors at Bolger Middle School, where Smith was a student, he said.

"AbbieGail was a wonderful young girl who was a Titan through and through," Niesz said. "She will be greatly missed by the entire Keansburg School District family, especially her friends and teachers."

Investigators with the prosecutor's office got involved in the investigation, at about 5 a.m. Thursday.

MaryAnn Spoto may be reached at mspoto@njadvancemedia.com. Follow her on Twitter @MaryAnnSpoto. Find NJ.com on Facebook.