PORTLAND – Authorities say the investigation into Amy St. Laurent’s death remains active although police are keeping quiet about developments in the case.

The 25-year-old South Berwick woman disappeared Oct. 21 after a night out in Portland. Her body was found in a shallow grave in Scarborough in early December.

The death was ruled a homicide, but authorities will not say how she was killed. “In this type of a case, what we’ve learned over the last three months, some of that information is best held among ourselves because only investigators and the person or persons responsible for her death know the real story,” said Stephen McCausland, spokesman for the Maine State Police.

While the fever pitch of the police investigation has subsided, a handful of detectives and prosecutors continue working on the case. At one point, dozens of officers scoured the woods between Portland and St. Laurent’s home in South Berwick while helicopters and Coast Guard vessels patrolled the skies and waters in search of her body and clues.

Two detectives remain assigned to the case full time, said Portland police Lt. Joseph Loughlin. Police also are working closely with the Maine Attorney General’s Office, which ultimately will prosecute the homicide.

So far, no one has been charged in St. Laurent’s death. The man identified as the primary suspect in court documents by a probation officer is in jail but has not been charged in the homicide.

“This is an open case and will remain so until someone is charged,” McCausland said. “Portland and state police have been working on this case closely and continue to do so.”

Four days after her body was found, police arrested Jeffrey “Russ” Gorman after an armed standoff in Troy, Ala. Gorman was identified in court documents by a probation officer as the primary suspect in St. Laurent’s death. St. Laurent’s body was found a half-mile from the home Gorman shared with his mother.

But Gorman has only been charged with probation violations, and police will not identify suspects or confirm whether Gorman was the same person last known to have seen St. Laurent.

Early in the investigation, police said a man claimed to have driven St. Laurent from the Pavilion nightclub in downtown Portland to an apartment on Brighton Avenue. He told police he dropped her off in front of the club about an hour later, after the club had closed.