LISBON — The medical condition of a 17-year-old stabbing victim from Lisbon was upgraded Thursday from critical to fair, a spokeswoman at Maine Medical Center in Portland said.

The teen, injured Tuesday night on Beech Street in Lisbon, was rushed to Central Maine Medical Center in Lewiston where he was stabilized before being taken to the Portland hospital Wednesday.

A Maine State Police spokeswoman said Thursday that the agency’s Major Crimes Unit-South had been investigating the incident due to the severity of the boy’s injuries. The unit investigates homicide cases that are prosecuted by the Maine Attorney General’s Office.

With the improvement of the teen’s condition, state police turned its investigation back to Lisbon officials, the spokeswoman said.

Police Chief Ryan A. McGee said Thursday that the special state police unit had been assisting local police in the investigation.

Matthew Newton-Fortin sits in Androscoggin County Jail in Auburn on Wednesday during his initial appearance in 8th District Court in Lewiston. Christopher Williams/Sun Journal

Matthew Newton-Fortin, 18, of Lisbon was charged Wednesday with elevated aggravated assault in connection with the stabbing. The felony is punishable by up to 30 years in prison.

Newton-Fortin appeared in 8th District Court in Lewiston on Wednesday via videoconference from Androscoggin County Jail in Auburn where he’s being held in lieu of $75,000 bail.

A judge assigned Lewiston attorney George Hess to Newton-Fortin’s case.

No plea was entered Wednesday because felony cases must be presented to a grand jury. If it hands up an indictment a plea can be entered and the case proceed to trial.

No further details of the incident were released by McGee.

Judge Brent Davis impounded an affidavit written by police that provided details to support probable cause for Newton-Fortin’s arrest. The judge ruled Wednesday that there was probable cause to support the charge.