Police in Virginia and Maryland have identified additional suspects in separate MS-13-related killings, part of a wave of recent violence tied to the resurgent street gang.

Prince William County police in Virginia said Thursday that they are looking for Dimas Misael Canales Santos, 27, of Hyattsville, Md., and have arrested a 17-year-old from Maryland in connection with the slaying of Christian Alexander Sosa Rivas, whose body was found near the Potomac River in the Dumfries area of the county in mid-January. Sosa Rivas, 21, was from Fairfax City, Va.

Police had previously made six arrests in the killing, which authorities think was carried out because Sosa Rivas angered local leaders of MS-13 — shorthand for Mara Salvatrucha — by claiming to be a leader in the gang, according to a search warrant. Charging documents say that around New Year’s Eve, female associates of MS-13 used social media to lure Sosa Rivas to the location where he was killed.

Montgomery County police in Maryland also announced Thursday that they had made a fifth arrest in the killing of Cristian Antonio Villagran Morales, 18, who was stabbed more than 40 times, allegedly by MS-13 members, in a Gaithersburg, Md., park in July. Jose Coreas Ventura, a.k.a. Josue Corea, 20, was taken into custody in Bedford County, Va., after allegedly fleeing arrest. He is charged with first-degree murder.

One of the suspects told police that Villagran Morales was killed because he was a member of a rival gang, but detectives said there was no evidence of that.

The Sosa Rivas case has ties to the MS-13-related killing of 15-year-old Damaris A. Reyes Rivas, who was taunted, interrogated and then killed in a Springfield, Va., park about a week later in retaliation for Sosa Rivas’s killing, according to a search warrant. Her assailants took videos of the killing, and one attacker brazenly wore a court-issued GPS monitoring bracelet, according to a search warrant. Reyes Rivas’s body was discovered a short distance from the park near an industrial area in mid-February.

In all, police have arrested or issued warrants for 18 suspects in the Sosa Rivas and Reyes Rivas slayings. Nearly all are teens or young adults, a fact that has troubled local law enforcement officials.

“The most alarming thing we see these days is violence by young adults,” Jay Lanham, director of the Northern Virginia Regional Gang Task Force, said at a meeting on the violence Wednesday night in Fairfax County.

At the packed forum in Annandale, Va., Fairfax County detective Douglas Comfort said the county had recorded a 70 percent increase in MS-13 violence from 2015 to 2016, part of a regional increase in activity by the gang. Fairfax County gang detectives said in an interview that the gang is rebuilding after a major federal case in 2014 that sent some top leaders to prison.

The 17-year-old from Montgomery County was arrested on suspicion of murder and conspiracy to commit a felony. He has been charged with being a principal in the second degree to a murder. Police said that authorities will seek to extradite him from Maryland to Virginia to face charges.