Authorities believe the four males, ranging from ages 16 to 20, were killed several days ago in a park in Central Islip, a working-class community about 47 miles east of New York City. Suffolk County Police found the bodies late Wednesday in a wooded area. It wasn't immediately clear what led them to the park.
The victims "suffered from significant trauma throughout their body with a sharp or edged instrument," county Police Commissioner Timothy Sini said.
"The manner in which they were killed is consistent with the modus operandi of MS-13," Sini told reporters.
MS-13, also known as La Mara Salvatrucha, is one of the largest criminal organizations in the United States, with more than 6,000 members in at least 46 states and the District of Columbia, the US Attorney's Office said.
In addition, more than 30,000 MS-13 members operate internationally, mostly in El Salvador, Mexico, Honduras and Guatemala.
MS-13 uses violence to intimidate rival gangs, using weapons ranging from firearms to machetes.
Sini said police are not ruling out any possibilities in the investigation. He announced a $25,000 reward for information that helps solve the case.
One family told CNN affiliate WPIX
it believed their missing teenager was among the dead. Police have not released the victims' identities.
'This is a long-term war'
The discovery of the bodies comes about a month after more than a dozen MS-13 members were indicted in seven killings
on Long Island over three years, including the deaths of several high school students last year.
Two of the students -- Nisa Mickens, 15, and Kayla Cuevas, 16 -- were beaten with baseball bats and a machete in September in nearby Brentwood.
Kayla had been involved in "disputes" with MS-13 gang members and associates, including a recent altercation at Brentwood High School, where the girls attended classes. The girls had gone for a walk the night they were killed, CNN affiliate News 12 Long Island
A third Brentwood High School student, Jose Pena, 18, was killed on June 3 because he had been suspected of violating gang rules, authorities said. His remains were discovered in October.
The gang, which federal authorities said is a "transnational criminal enterprise," became so powerful that the FBI started a MS-13 National Gang Task Force in 2004.
"We're under no illusion that MS-13 is still operating in Suffolk County. No doubt, we've made tremendous progress," Sini said.
He added: "But this is a long-term war. And make no mistake about it, it's a war," Sini said.