State Police assigned to Suffolk County District Attorney Daniel F. Conley’s office and MBTA Transit Police are investigating an early-morning collision that left a 54-year-old pedestrian in intensive care.

State Police homicide detectives and MBTA Transit Police responded to the area of Huntington Avenue and Ring Road in Boston’s Back Bay shortly after 2:00 a.m. On arrival, they observed an MBTA bus that had been travelling westbound on Huntington Avenue when it apparently struck the male victim. Also responding were members of the State Police Crime Scene Services Section and Collision Analysis and Reconstruction Section.

State Police are currently assisting in the investigation. They will take the lead if the man succumbs to his injuries. He is currently in the intensive care unit of Boston Medical Center.

Preliminary findings suggest that the bus was travelling at a low rate of speed at the time of the collision. Civilian witnesses told investigators that the victim was seen running toward the bus as the bus was turning onto Ring Road. The operator of the bus told investigators that he felt an impact and immediately stopped the bus.

Investigators did not immediately detect the signs of alcohol or drug impairment, but the driver, 50, will be tested for such impairment under MBTA policy. He has been with the MBTA for five years.

Neither the operator of the bus nor the injured man is being identified at this time.