Damaris A. Reyes Rivas, 15, whose body was discovered by police in Springfield on Feb. 11. (Family photo)

Ten suspects have been identified in connection with the gang-related slaying of a 15-year-old Gaithersburg girl who was held against her will, assaulted and then killed at a Virginia park in January, Fairfax County police said Wednesday.

The six juveniles and four adults, ages 15 to 21, are all believed to have been involved in the death of Damaris A. Reyes Rivas, police said. Nine are in custody, and police said they are looking for the 10th, a 16-year-old girl.

The suspects in custody have been charged with abduction and gang participation, but police said they expect to file murder charges in the case as soon as Thursday.

Damaris voluntarily left home on Dec. 10, touching off a two-month investigation that now includes possible connections with at least three other cases — those of two teenage girls who disappeared but have returned to their Fairfax County homes and the slaying of a 21-year-old man in Prince William County.

(Claritza Jimenez/The Washington Post)

Police said they believe that Damaris probably was killed about Jan. 8 in Springfield’s Lake Accotink Park and that her body was dumped nearby, where it was discovered by police over the weekend. Police said video evidence led them to believe that Damaris was in trouble, but they did not disclose its nature.

Maria Reyes, Damaris’s mother, said Wednesday that she is relieved arrests have been made, but she still has more questions than answers.

“I’m still confused,” Reyes said. “I need to ask them why they killed my daughter. She didn’t owe them anything, so why did they kill her?”

At a Wednesday news conference, police declined to comment on a motive for Damaris’s slaying or the larger threads connecting the multiple cases.

The adults arrested were Cindy Blanco Hernandez, 18, of Reston; Wilmer A. Sanchez-Serrano, 21, of no fixed address; Aldair J. Miranda Carcamo, 18, of Springfield; and Jose Castillo Rivas, 18, of Springfield. The juveniles were not identified.

It was unclear whether any of the adults had attorneys as of Wednesday evening. Family members could not immediately be reached.

Police would not identify which gang is suspected in the slaying, but Reyes said that her daughter had fallen in with a local clique of MS-13. There has been a resurgence in violence by the gang in the D.C. suburbs in recent years, and its members have been linked to killings and other crimes.

After Damaris left home, she maintained contact with her mother via Facebook, and her case began as that of a missing person. On Jan. 4, Reyes said, she finally reached Damaris by phone and begged her daughter to come home, but Damaris said, “I can’t.”

Police and Reyes believe Damaris was likely involved with gang members and was killed just days later.

Police said they are exploring the connections between Damaris’s slaying and the disappearance and return of two other teenage girls. Police said one of the girls, Venus Romero Lorena Iraheta, 17, of Alexandria, was possibly in danger before she returned home safely Tuesday night. She was later interviewed by detectives and was an acquaintance of Damaris, police said.

Prince William County police also revealed for the first time Wednesday that Iraheta’s case was linked to the killing of a 21-year-old man in Prince William County. The body of Christian Alexander Sosa Rivas was found along the Potomac River in Dumfries on Jan. 12.

Sgt. Jonathan Perok, a Prince William County police spokesman, declined to discuss the nature of the link between the cases, but said Iraheta and Rivas were acquaintances. In an interview with NBC 4 on Tuesday, Iraheta said that she left home because she was distraught over the death of a former boyfriend. Iraheta left on Jan. 15.

Fairfax County police are also looking at connections to another case. Lizzy Rivera Colindres, 16, of Springfield was also reported missing on Jan. 15 and left home voluntarily with her 5-month-old son, police said. She returned last weekend.

Police said the case is not directly connected to Damaris’s killing, but the baby’s father is among those suspected in Damaris’s killing and Colindres may have left home in fear of him.

On Monday, Lynchburg police arrested the baby’s father, 18-year-old Jose Castillo Rivas, on an abduction charge stemming from an incident in which he allegedly attempted to get Colindres to drop a restraining order against him after a Jan. 10 court hearing.

Officer Tawny Wright, a Fairfax County police spokeswoman, said detectives do not think the cases pose a general threat to the public. Police said they think they have identified all the suspects in Damaris’s disappearance and death and know of no other missing girls.

“There is no public safety threat,” Wright said. “The kids that are involved in this are acquainted and affiliated. We don’t think they are going to outside groups who are not already affiliated with this group.”

In January, Montgomery County police said detectives in Fairfax County began to think that Damaris might have been hanging around gang members. Montgomery detectives were told of the development on Jan. 15, police said.

Fairfax County police said they had searched Lake Accotink Park on a handful of occasions before Damaris’s body was found Saturday.

Reyes said she didn’t know whether her daughter knew Iraheta or Colindres, the other teen girls who had been missing. She never saw or spoke to them. But she said she learned from her niece that it was a female friend who picked up Damaris from her home the night she disappeared.

Reyes said she thinks her daughter also dated Christian Alexander Sosa Rivas, the young man found dead in Prince William County last month.

On Monday, Damaris’s death was ruled a homicide. She had suffered trauma to her upper body.

Maria Reyes said she was haunted by the fact that her daughter’s body had lain for weeks so close to where she had searched for her.

“I went everywhere looking for her. I looked in those places,” she said, her voice breaking. “How could I not find her? How? How?”

Dana Hedgpeth, Jennifer Jenkins, Dan Morse and Julie Tate contributed to this report.