A couple originally from China and their two elementary school-age boys were found fatally stabbed and bludgeoned in their modest suburban home just over a year ago.

Investigators since then have run into language barriers, cultural differences and the logistical challenge of a quadruple murder case with tendrils running through Manhattan's Chinatown and possibly beyond. They've looked at an eerily similar family slaying in Mississippi and have reached out across the nation and the globe.

The investigation remains wide open.

"There's nothing that we're not looking at," New York state police Senior Investigator John Camp said recently. "We're trying to see: Is it human trafficking? Is it money laundering? Is it gang related? We're basically leaving no leaf unturned."

Police were called to the small home on a busy commercial road on Oct. 8, 2014 by a concerned 911 caller. Inside were the bodies of Jin Chen, 39, his wife, Hai Yan Li, 38, and their sons: 10-year-old Anthony and 7-year-old Eddy. Police later said the victims were stabbed and attacked with a hammer.

The couple came over from the Fujian province of China years ago and their children were born in the United States, said Eddie Chiu senior adviser of Chinatown's Lin Sing Association, which helped relatives with funeral and travel arrangements.

The family settled into a tidy suburb adjacent to Albany, where Chen worked part-time at a Chinese take-out restaurant less than a mile down the road. But details about his professional life remain murky. Police will not comment on media reports that he was involved the shadowy world of undocumented Chinese workers.

Camp said investigators are moving in multiple directions and travel regularly to Chinatown, where the victims had family connections.

It has not been easy.

Detectives have repeatedly run into the language barrier and many interviews are conducted with translators on loan from the FBI. Police say they are simply not getting the volume of tips they would normally get for such a heinous, high-profile crime, even as the district attorney promised immunity from immigration charges to reluctant witnesses.

It's likely that the brutal nature of the killings combined with the immigration status of some potential sources is deterring cooperation with police. Chiu said cooperation can be hard to come by in Chinatown.

"Everybody's scared. This is Chinatown. Nobody wants to talk," he said.

Though short in cooperation, the investigation remains broad in scope.

Investigators seeking insights have reached out to police in cities with large Asian populations, including Chicago, Los Angeles and Montreal. They have worked with New York City police and the FBI. They have made indirect contact with law enforcement in China, mostly through the State Department, Camp said.

And they have talked to police in D'Iberville, Mississippi, north of Biloxi, where there was a separate, unsolved murder of a Chinese family. The 2011 Mississippi case involves the fatal stabbing of a couple who owned a Chinese restaurant and the wife's sister.

While there are similarities, police have not found a connection between the New York and Mississippi murders.

Camp said he has three investigators still working the case who receive help as needed. Law enforcement made a public plea last month as the investigation entered its second year.

"Somebody out there must know something," Camp said.