Maria Reyes, shown in Gaithersburg, Md., on Feb. 14, holds a dress her daughter, Damaris A. Reyes Rivas, was going to wear for her quinceañera. (Dan Morse/The Washington Post)

The remains of two apparent murder victims were discovered in a Northern Virginia park, and police are exploring whether the deaths are related to a resurgent MS-13, a gang that has ties to a wave of violence the Fairfax County police chief called “out of control.”

The grim discovery, announced Friday, comes as several suburban counties outside the nation’s capital are grappling with an increase in bloodshed linked to the street gang.

In recent weeks, two young people, a 15-year-old Maryland girl and a 21-year-old man she had dated, were slain in Virginia, allegedly by gang members. In all, 16 people, many of them teenagers, have been arrested in those two cases.

Fairfax Police Chief Edwin C. Roessler Jr. pleaded with parents to look for signs that young people are involved with gangs as he discussed the discovery of the two as yet unidentified bodies buried in Holmes Run Park, where two people killed by the gang were found in 2014.

“This problem is horrible,” Roessler said. “This is four murders in this park. Obviously, we’ve had other murders in the region in the past few weeks. This is getting out of control.”

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

Timothy Slater, special agent in charge of the criminal division for the FBI’s Washington field office, said the D.C. region is one of a number of MS-13 “hot spots” across the country. Others are in New York and Texas.

Local gang experts said MS-13 leaders in El Salvador have been pushing for changes in the leadership of the gang in the United States, prompting more violence. They also said the record numbers of unaccompanied minors coming across the border with Mexico helped swell recruitment.

Authorities said they have been surprised by the young age of some MS-13 members carrying out attacks and reprisals against other members.

“The gang starts them on lesser crimes before moving them on to more violent activities,” said Douglas W. Keen, the chair of the Northern Virginia Regional Gang Task Force. “Their attitude is, ‘Once we get you in, you’re ours.’ Everyone is disposable to them.”

[Va. police: Death of teenage girl, two other cases may all be gang-related]

Roessler said the bodies found in the Lincolnia-area park on Thursday were transferred to the state medical examiner for autopsy and identification. Police began searching Holmes Run and a park in Falls Church for human remains Wednesday after the county’s gang unit received a tip.

Police believe the bodies had been in the park for less than a year and asked for the public’s help in locating those responsible for what are believed to be slayings. Police say they are still exploring whether the individuals were killed in Holmes Run or somewhere else. They also do not yet know whether the case is connected to ongoing MS-13 cases in the areas.

Police remove crime scene tape March 3 in Fairfax County from the area in Holmes Run Park where two sets of human remains were found. (Evelyn Hockstein for The Washington Post)

The remains were found in the woods on a steep incline a few hundred feet behind a quiet cul-de-sac of residential homes. One body was buried at the top of the hill, the other at the bottom.

As police investigated the new case, fresh details also emerged Friday in two other slayings linked to MS-13 that authorities believe are related — the killing of Gaithersburg 15-year-old Damaris A. Reyes Rivas and Fairfax 21-year-old Christian Alexander Sosa Rivas.

[Timeline: Web of gang-related activity in Va., Md.]

Ten people, including six juveniles, have been arrested in the abduction and slaying of Damaris, whose body was discovered near an industrial area in Springfield in mid-February. Damaris had left home in mid-December, and her mother said she had fallen in with an MS-13 clique.

People familiar with the prosecution’s case said that the teen was lured to a nearby park on or around Jan. 8 on the pretext of smoking pot but that when Damaris arrived she was removed from a car by alleged MS-13 members and walked into the woods. Damaris grew alarmed and blurted out at one point, “I have been set up,” people familiar with the case said.

Damaris was taken to an MS-13 hangout near a set of train tracks, the people said. At that point, a juvenile charged with murder in Damaris’s case allegedly walked her down an embankment and interrogated her. The Washington Post generally does not name juveniles charged in crimes.

The teen asked Damaris whether she had a relationship with Sosa Rivas, people familiar with the case said the prosecution’s account shows. Damaris’s mother has said her daughter dated Sosa Rivas. The teen who confronted Damaris also knew Sosa Rivas and had a relationship with him at one point, authorities have said.

Damaris asked for forgiveness, but the other teen allegedly slashed her with a bowie knife, people familiar with the case said. Fairfax County police later determined that Damaris died of multiple forms of trauma to the upper body. Video evidence is among the clues in the slaying.

Every attorney for those charged in Damaris’s killing, except one, declined to comment. Vernida R. Chaney is representing one of the juveniles. “I think the evidence will show that not all of them are involved in the crime,” Chaney said.

Last week, Prince William County police announced the arrest of six people in connection with the slaying of Sosa Rivas, whose body was found along the Potomac River in Dumfries on Jan. 12.

Court documents in the case claim that two women charged used social media to lure Sosa Rivas to the Dumfries area where he was killed by MS-13 members.

Citing a search warrant that has since been sealed, NBC 4 reported that Sosa Rivas may have been targeted by fellow MS-13 members because he was claiming to be the leader of a local clique. The search warrant said Damaris was one of the last people to see him alive.

Two men charged in Sosa Rivas’s case were arraigned in Prince William County General District Court on Friday and were held without bail. Attorneys for defendants in the Sosa Rivas case declined to comment or did not respond to requests.

MS-13 violence has flared across the country. In Houston this past week, two alleged gang members were charged with killing a 15-year-old girl and holding her 14-year-old friend captive.

In Brentwood, N.Y., where MS-13 activity has likewise spiked, prosecutors on Thursday charged 13 alleged gang members in seven slayings.

“As the MS-13 continues its efforts to expand and entrench itself in our communities, both by sending gang members to illegally enter the United States from Central America, and by recruiting new members from our schools and neighborhoods, [we] will continue our mission to dismantle the MS-13 and free our neighborhoods from the terror they cause,” U.S. Attorney Robert L. Capers of the Eastern District of New York said in a statement.

Dana Hedgpeth and Michael E. Miller contributed to this report.