State Police, Boston Police, and Suffolk County prosecutors are reminding residents and local colleges to use caution along the Charles River Esplanade in light of a sexual assault reported in that area last night.

The reminder comes after a student at an area college reported being assaulted as she sat on a park bench near Massachusetts Avenue at about 11:30 p.m. The assailant is described as a black male about 25 to 30 years old, 6’1” to 6’2”, about 230 lbs, with short hair and a missing front tooth. He was wearing black sweatpants and a green top. The man is said to have engaged the student in a lengthy conversation before assaulting her. She fled the area on foot and reported the assault after going to a friend’s residence to call Boston Police.

Suffolk County District Attorney Daniel F. Conley, State Police Colonel Marian McGovern, and Boston Police Commissioner Edward Davis recommended that joggers, cyclists, pedestrians, and others travel in groups if they visit the Esplanade at night. More specifically, they recommended that people in the area remain alert and aware of their surroundings, avoid one-on-one contact with strangers in the area, seek help if a stranger tries to isolate them, and not accept rides from strangers.

The identity of the assailant in last night’s case remains under investigation by State Police from the Boston barracks, troopers assigned to the Suffolk DA’s office, and Boston Police. Though the Esplanade is state property, city investigators are taking an active role in the probe in light of a series of unsolved but linked late-night sexual assaults along the Esplanade and in South Boston. Investigators have not determined whether last night’s assault is linked to the earlier attacks.

The South Boston assault took place in Joe Moakley Park at about 3:00 on the morning of July 29, 2006. The Esplanade assaults took place between 11:00 p.m. and 3:30 a.m. on June 16, 2007; July 29, 2007; and July 14, 2009. The victims collectively described the assailant as a black male in his mid-20s to mid-30s standing 5’8” to 5’10” tall with a medium to large build and a bald head.

Anyone threatened or attacked on the Esplanade or elsewhere can call 911 from a cell phone and be immediately connected to a State Police communications center. Anyone with information on the prior assaults is urged to call the State Police Boston Barracks at 617-727-6780.