Maria Reyes holds a dress her daughter Damaris was going to wear for a Sweet 15 Quinceanera celebration on Jan. 28. (Dan Morse/TWP)

The killing of one teenage girl and the disappearances of two others who have since returned home may all be connected and may be gang-related, Fairfax County police said Tuesday.

Police said that people are in custody in connection with the cases on gang-related charges but that investigators are still trying to determine what additional charges to file against each of the suspects.

They declined to identify the individuals in custody or the charges and possible motives. They also would not identify what gang is suspected in the incidents.

“These kids are part of a big social network, and some are more acquainted than others,” said Officer Tawny Wright, a Fairfax police spokeswoman. “We are trying to sort that out before we press more charges.”

The cases burst into public view after the discovery Saturday of the body of 15-year-old Damaris A. Reyes Rivas of Gaithersburg. Her body was discovered by Fairfax police near an industrial park in the Springfield area, and police said she appeared to have been dead for roughly a month.

Venus Lorena Romero Iraheta, 17, left her home voluntarily on Jan. 15, police said. She was an acquaintance of 15-year-old Damaris A. Reyes Rivas, whose body was discovered by police in Springfield on Saturday. (Fairfax County Police, Family photo)

Damaris’s mother, Maria Reyes, told The Washington Post on Tuesday that her daughter had fallen in with a local clique of MS-13, before her disappearance from the family home Dec. 10.

On Jan. 6, Damaris appeared to have been sent warnings that gang members wanted to kill her, according to Facebook messages her mother shared with The Post.

“Those suckers want to kill you,” read one Facebook message, while another added, “They have already given permission to take you out.”

The violent MS-13 street gang has had a resurgence in the Washington suburbs in recent years. Its members have been linked to killings and other violent crime.

At a Tuesday afternoon news conference, Fairfax police pleaded for the public’s help in locating Venus Lorena Romero Iraheta, 17, of Alexandria, who was still missing then and who police said might be in danger. Police said Tuesday night that she had returned home safely about 9 p.m.

Police said that Iraheta was an acquaintance of Damaris and that Iraheta had voluntarily left home Jan. 15 with a black and red backpack full of clothes. Police declined to say why they thought Iraheta had been at risk, but they said the information was developed after interviews with various people Tuesday.

The third case that Fairfax police said may be related involves a young Springfield mother, Lizzy Rivera Colindres, 16, who recently returned home with her 5-month-old son after going missing in mid-January.

Lynchburg police announced that they had assisted in the arrest of 18-year-old Jose Ivan Castillo-Rivas at a hotel on Monday. Wright, the Fairfax police spokeswoman, said Castillo-Rivas had been charged with abduction after he tried to force Colindres to drop a restraining order against him on Jan. 10. She went missing from her home five days later and police said it might have been out of fear of Castillo-Rivas. Police announced last weekend that Colindres had returned home.

At her home in Gaithersburg, Reyes mourned the daughter who had come to the United States in 2014 from El Salvador, following her mother’s arrival a decade earlier.

Reyes said that she had come to this country in 2005 to get away from gang violence but that Damaris met gang members at a Montgomery County public school.

“I fled from these types of people in El Salvador,” Reyes said. “But when she came here, she found them at school, started going out with them and even fell in love. She was just a girl of 15 who didn’t know anything. They were older.

“They walk around here and nobody realizes, or if they realize it they don’t do anything about it,” Reyes said of MS-13.

Reyes said that for reasons she didn’t know, her daughter had a falling out with some members of the gang last year.

She tried pulling her daughter out of school and planned to send her to live with her father in Houston, but said Damaris disappeared before her mother had a chance to get her out of harm’s way.

She awoke Dec. 10 and found her daughter had gone. Clothes were missing from her closet. Reyes’s niece told her that Damaris had left in the middle of the night.

Reyes called her daughter, but there was no answer. She said she then called police, but she said she felt like officers didn’t take her seriously at first.

Capt. James Humphries, commander of the Montgomery Police Department’s Special Victims Investigation unit, which handles missing children cases, said a Spanish-speaking detective was immediately assigned to the case, and later was joined by a second detective. That second detective, John Witherspoon, stopped by the Reyes’s home on Tuesday to check on Reyes and other family members.

For weeks after her daughter’s disappearance, Reyes sent Damaris messages on Facebook asking her to come home. She said she only received a one-word response: “Why?”

On Jan. 4, Damaris finally picked up the phone. Reyes begged her daughter to come home, but Damaris said, “I can’t.”

“That was the one and only time I spoke to her,” Reyes said.

About two weeks ago, Reyes was so desperate that she went to a house belonging to gang members and asked for her daughter, but they said they hadn’t seen Damaris. A few days later, Reyes’s car was stolen, she said.

“I suppose that was them trying to send me a message,” she said.

Capt. Paul Starks, a Montgomery County police spokesman, said that from the time Damaris was reported missing on Dec. 10, police actively worked the case.

The department did not issue a news release as it does in some of the 990 missing juvenile reports it receives every year. Starks said detectives did not do so in the case because, initially, they thought more targeted efforts would be more effective and later grew worried that they might impede investigations underway in Fairfax.

But Starks said Montgomery County police also will review the case to see what steps could have been done differently.

In January, Montgomery police posted fliers near her home in Gaithersburg and in areas of Northern Virginia where they thought she was staying. The fliers also were posted on Damaris’s Facebook page and on the Facebook page of Damaris’s mother, Starks said.

Damaris had run away in the past and returned, police officials said, most recently in November. While away, she generally stayed in touch with her mother over the phone, as she did in December and January, police said.

Montgomery detectives advised her mother on what to say. “We got involved from the beginning. We were helping coach her on what to say,” Humphries said.

Detectives tried to text Damaris, but she wouldn’t return their texts. The detectives spoke with her friends, who told them that she was okay but that she didn’t want to come home, Humphries said. Damaris also stayed active on social media.

In this case, Humphries said, using those techniques and the fliers was deemed a more effective strategy than issuing a news release to media outlets.

In January, Starks said detectives in Fairfax County began to believe Damaris might have been hanging around gang members. Montgomery County detectives were told of the development on Jan. 15, Starks said. The spokesman said that at that point, Montgomery detectives had grown concerned about compromising investigations in Fairfax. But he said the decision was made within the Montgomery department not to issue a media release about Damaris.

Fairfax County police said they had been to locations near Lake Accotink Park in Springfield a handful of times in recent weeks, searching for signs of Damaris, before her body was discovered.

Authorities said she suffered trauma to the upper body.

When police told Reyes they had found her daughter’s body, the mother’s fears were confirmed.

“She was a sweet person, a good person, kind and well educated. Her teachers loved her,” said Reyes. “Why did they kill her?”

Rachel Weiner and Eddy Palanzo contributed to this report.