Police declined to comment on the arrests, saying more could be forthcoming.

Fairfax County police said at a news conference last week that information that turned up during the Rivas investigation led them to conclude that a missing Maryland teenager had been killed. Her remains were found this month near an industrial park in Springfield.

Fairfax County Police Chief Edwin Roessler Jr. said Damaris Reyes Rivas, 15, of Gaithersburg, Md., who left home in mid-December, was held against her will near an industrial park, assaulted and killed in a “savage and brutal” fashion about Jan. 8. Her body was discovered Feb. 11 by police, just one day before the first arrests in the Rivas case.

Police said video evidence was among the clues in the killing.

Reyes Rivas’ mother said her daughter had become involved with the MS-13 gang. She also said her daughter had dated Rivas. They are not related.

The mother said her daughter had come to the U.S. from El Salvador in 2014. She showed a reporter messages her daughter had received on Facebook, saying “those suckers want to kill you” while another added, “They have already given permission to take you out.”