The body was first found by the driver, which makes him the prime suspect
Investigators are yet to solve the mystery behind the Chinese man's body, found buried in the garden of his apartment complex on Wednesday.
Police said their first suspicion was that the deceased, Gaojian Hui, was involved in an extra marital relation, however, his wife denied the allegation.
Dhaka Metropolitan Police (DMP) Gulshan Division Additional Deputy Commissioner (ADC) Abdul Ahad said: "We questioned Gaojian's wife in different ways. She does not know why the incident occurred and could not give us any clue."
"It is clear that the Chinese man was strangled to death in his own flat and it is a pre-planned murder. We are investigating to find out why he was killed, who were involved and how the body was buried," he added.
This official also said they found out the cctv cameras of the building to be out of order since October 23, which creates another mystery.
The ADC said: "We have been interrogating six suspects, including the victim's driver Sultan, house help Farida Akter, his translator and one night guard of the building.
"However, we still could not extract any important information from them. We are waiting for the autopsy report, followed by more interrogation of the six suspects."
The deceased Gaojian Hui, 48, was a stone importer who had been living with his family in a flat in Dhaka's Banani area for the last one year. The deceased's family members had travelled to China in November and came back to Bangladesh on Thursday.
Banani police station Officer-in-Charge (OC) Nure Azam Miah, said Gaojian's friends filed a murder case against an unknown murder on Wednesday night.
According to the investigation officers, driver Sultan was the first one to find Gaojian's body, which makes him the prime suspect.
Sultan claimed that he found his boss's body after looking for him for 2 to 3 hours.