US police say Chinese citizens 'executed' at marijuana farm

US police have identified a suspect in the weekend slayings of four people at an Oklahoma state marijuana farm but said they aren't releasing a name because doing so could put more people in danger.

Authorities said the three men and one woman, who were Chinese citizens, were "executed" on the 10-acre property west of Hennessey town, about 90 kilometres northwest of Oklahoma City. A fifth victim who was wounded and who is also a Chinese citizen was taken to an Oklahoma City hospital.

The next-of-kin notification was still pending "because of a significant language barrier," police said.

Authorities have a suspect in mind, but the Oklahoma State Bureau of Investigation is withholding the name, for now, to avoid endangering others.

"The suspect was inside that building for a significant amount of time before the executions began," OSBI said in a news release Tuesday. "Based on the investigation thus far, this does not appear to be a random incident."

'There's a lot to unravel'

OSBI Captain Stan Florence said the previous day that authorities believe the suspect knew the victims, who were found dead Sunday night.

"They all know each other," Florence said. "Don’t know if they’re related, or if they’re coworkers, but certainly these individuals were, we believe, all familiar with each other."

Authorities have not identified the victims or said how they died. The case is being investigated as a quadruple homicide.

Police searched the property late Sunday and Monday, using drones and helicopters and on the ground, but did not find the suspect, Florence said.

"There's a lot to unravel with this case," he said. "It’ll take a little time for us to process it."

Porsha Riley, the spokesperson for the Oklahoma Medical Marijuana Authority, said there is an active license for a medical marijuana grow business at the location.

Oklahoma voters legalised medical marijuana in 2018, and the industry quickly boomed thanks to an open-ended law that put in place fewer restrictions than in other states.

In March, voters will decide whether to legalise the recreational use of the drug.