(ABC NEWS) -- Massachusetts investigators have developed what they call "mounting evidence," bolstered by "forensic hits," that point to the possible involvement of both Tamerlan Tsarnaev and his younger brother Dzhokhar in a gruesome, unsolved triple homicide in 2011, law enforcement officials told ABC News.
The officials cautioned that until more definitive DNA testing is complete, it is still too early to consider bringing an indictment against the younger of the two brothers, who officials said has admitted his role in the Boston Marathon bombings that killed three and injured 260 more on April 15. Tamerlan was killed in a shootout with police days after the Marathon bombing attack, but Dhzokhar survived and was captured.
Through a spokesperson, the newly-appointed Middlesex District Attorney, Marian Ryan, declined to comment on the brothers' possible involvement in the 2011 murder.
In the wake of the Marathon bombings, Middlesex County began to probe a link between the elder Tsarnaev and Brendan Mess, one of the three men killed in the gruesome slaying on Sept. 11, 2011.
Officials said Mess and two men were found in a Waltham residence with their throats slit and their bodies covered with marijuana. Tamerlan and Mess were once roommates and did boxing and martial arts training together.
Now law enforcement officials tell ABC News that some crime scene forensic evidence provided a match to the two Tsarnaev brothers. The officials also said records of cell phones used by the Tsarnaevs appears to put them in the area of the murders on that date. Several officials confirmed the new findings but declined to be identified because they are not authorized to comment on the ongoing investigation.
Miriam Conrad, one of the attorneys representing Dzhokhar Tsarnaev in the bombing case, declined to comment through her legal assistant.
The savage 2011 murders unfolded on a quiet dead-end street on a balmy night.
Mess and his friends, Erik Weissman, 31, and Raphael Teken, 37, had ordered dinner from Gerry's Italian Kitchen at 8:54 p.m., but when a delivery woman arrived twenty minutes later there was no answer at the door and no one answered a call to Weissman's cell phone, from which the order was placed.
The bodies were discovered the next day. Former Middlesex District Attorney Gerry Leone said at the time that the murders were "graphic." Other investigators called it perplexing.
Roughly seven pounds of marijuana was dumped on the bodies and $5,000 in cash was left behind. Neighbors said they did not hear any signs of trouble – even with open windows – and there was no forced entry. In a 2011 interview, Leone said investigators theorized there had been more than one person at the scene of the murders based on "many factors," but no suspects were identified.
From there the case went cold, until photos of the Boston Marathon suspects were released and family and friends of the Waltham victims recognized them and remembered Tamerlan's strange behavior after the murders. He did not attend his friend's funeral and vanished from the martial arts gyms where the men had sparred together.