Authorities are investigating a single-vehicle rollover crash on Morrissey Boulevard early Thursday morning that killed two occupants and injured two others, leaving one in “grave condition,” according to Massachusetts State Police.

A state trooper patrolling the treacherous roadway in Dorchester observed the vehicle, a 2013 Hyundai Accent, traveling at a “high rate of speed” on the northbound side before it crashed in the area of UMass-Boston.

The victims are all males, and three are believed to be teenage juveniles, State Police said in a release. Investigators are working to confirm the identities of the victims.

The crash prompted the response of additional State and Boston police patrols along with Boston Fire and EMS.

Responders determined one victim to be dead on scene, while the three others were taken to various Boston hospitals. One of the victims was pronounced dead at the hospital.

A third victim is in “grave condition” at the hospital, and the fourth is hospitalized with injuries considered not life threatening.

All lanes on Morrissey Boulevard reopened at about 7:30 a.m. after the rescue response and investigation caused a partial closure of the roadway.

The facts and circumstances of the crash remain under investigation by Troopers from the State Police Detective Unit for Suffolk County, State Police Collision Analysis and Reconstruction Section, State Police Crime Scene Services Section, and the State Police-South Boston Barracks.