A Maryland girl could face charges for allegedly helping plot an acquaintance's rape, police said.

Just after midnight on Sept. 2, an 18-year-old woman was opening the door to her home when she was grabbed from behind by three males, the Frederick Police Department said in a press release.

The suspects struck the victim, pulled her hair, put her in a vehicle and transported her to an unknown apartment in the area, where they proceed to rape her for several hours, police said.

The attack was not random, Frederick Police Sgt. Andrew Alcorn told ABC News.

A younger girl -- an acquaintance of the victim -- may have been involved in planning the crime, police said, referencing messages sent by the girl on social media before and after the alleged attack. She could later be charged with accessory before the fact as a co-conspirator to the crime, Alcorn said.

The victim told police she was held captive for several hours and raped by two of the males, whom she identified as high school classmates Edgar Chicas-Hernandez, 17, and Victor Gonzalez Gutierres, 19, police said.

She could not identify the third suspect, who had his face covered while he filmed the events, police said.

Before releasing her, the suspects threatened the victim with additional harm if she reported the crime to police. The victim reported the rape to police three days after she was kidnapped, police said.

Both Chicas-Hernandez and Gutierres were arrested last week without incident, police said. They were each charged kidnapping, first-degree rape, sodomy, and first- and second-degree assault, according to case documents.

PHOTO: Victor Gonzalez Guttieres, 19, was arrested and charged with allegedly raping a classmate in Maryland. (Frederick Police Department ) More

PHOTO: Edgar Chicas-Hernandez, 17, was arrested and charged with allegedly raping a classmate in Maryland (Frederick Police Department ) More

Chicas-Hernandez is being charged as an adult, Alcorn said. They have both had their initial court appearances but did not enter pleas, Alcorn said. It is unclear if either of them has retained an attorney.

Authorities are still searching for a third suspect, whose identity remains unknown.

Police are working with prosecutors to decide whether to charge the acquaintance, who is a juvenile and younger than the suspects and victim, Alcorn said, describing the case as "sensitive" and "serious."

"It's just as important to rule her out of investigation as it is to bring her in," he said.

Alcorn said he didn't know the exact extent of the conversation the younger girl had with the suspects.

The attack does not appear to be gang-related at this point, Alcorn said.

Alcorn said situations like this rarely happen in the city of Frederick and that authorities are "taking it very seriously."

Police did not release the identities of the victim or the acquaintance who may later be charged.