BOSTON (AP) – A car linked to the fatal shootings of four young men in the basement of a Boston home was recovered on Saturday, while Boston Police Commissioner Kathleen O’Toole said she won’t tolerate a “premature arrest” in the high-profile case.

The 1998 black Ford Escort hatchback, which was driven before the incident by one of the victims and may have been taken by a suspect, was found unoccupied on a street in Boston’s Dorchester neighborhood.

Tuesday night’s slayings in Dorchester pushed the number of murders in Boston this year to 71, the highest in a decade. The victims were Edwin Duncan, 21, Jihad Chankhour, 22, Christopher Vieira, 19, and Jason Bachiller, 21.

No suspects have been identified. Police have not offered a possible motive for the killings, but they do not believe it was gang- or drug-related. There were no signs of forced entry.

O’Toole, in a memo to her department on Saturday, warned officers about overreacting.

“A premature arrest in a homicide case may ease public concern and media pressure, but justice will only be served if the investigation conducted identifies the correct perpetrator(s) and leads to an air-tight conviction,” she wrote in the memo, which the department posted on its Web site.

O’Toole also said investigators should not be judged by a recent drop in the department’s clearance rate.

“I’m certain that the (department) could significantly increase the clearance rate by prematurely arresting possible suspects and cutting investigative corners in homicide cases, but neither Deputy (Superintendent Daniel) Coleman nor I will allow that to happen,” she said.

On Friday, O’Toole announced that federal authorities will assist homicide detectives in investigating the case. However, in her statement Saturday, the commissioner stressed that federal authorities “are not coming in to take over” the investigation.

“To even imply that is absurd,” she continued. “These valuable partners are simply standing at the ready to respond to Deputy Coleman’s requests if he has any need for their services. Why would we ever refuse that genuine offer of support?”