A computer belonging to a suspended Eskom supervisor has been seized by police following revelations that the slain power utility's employee, Thembisile Yende, had lodged a complaint against him.

Yende's brother Mboneni Yende told Sowetan yesterday that they were aware of the complaint against the supervisor but were not familiar with its content.

"What we know is that she did confide in her mother about her unhappiness at work. She also forwarded the complaint to Eskom management at the head office in Megawatt Park [in Sandton, Johannesburg] complaining about tensions at work with her supervisor," he said.

A police source close to the investigation said the computer was seized last week from the Pieterboth substation in Springs, Ekurhuleni, where Yende was found dead.

Yende's body was found 13 days after she went missing. She disappeared on May 17 at the substation, where she had gone to work.

The police source said a few other employees at the substation and head office were also interrogated. "At the moment there is no specific suspect as the police are still connecting the dots and hopefully the seized computer will lead to a breakthrough.

"Amongst those interrogated are security guards who were on duty at the substation on the day she died."

Yende's friend - who asked not to be named - said she knew about the letter in which Yende complained about her supervisor. "I'm aware of the letter. I have seen it ..." she said.

However, police spokesman Captain Kay Makhubele said he could not confirm or deny the seizure of the computer or the existence of the letter.

Eskom spokesman Khulu Phasiwe said yesterday: "The police are investigating all the issues pertaining to Ms Yende's death, and Eskom is supporting them in getting to the bottom of this matter."

Last week, Yende's autopsy revealed that she had been killed, and that she sustained head and neck injuries.

When Yende went missing at the substation on May 17, she was working as a trainee technician for the power utility.

She joined Eskom in 2015.