A 58-year-old woman, her two sisters, and her brother-in-law were found dead in an apartment in Gujarat's Surat city on Saturday, police said.

Prima facie, they have died due to asphyxiation as the gas-powered geyser was left running. But the exact cause of death is yet to be ascertained, Deputy Commissioner of Police (DCP) R P Barot said.

The police were informed about the bodies around 9 am, he said.

Bodies of the flat owner, Jasuben Vadhel, her sisters Shantaben Vadhel (53) and Gauriben Mevad (55) and Gauriben's husband Hirabhai (60), were found in the apartment, the official said.

The victims had gone to bed around 10 pm on Friday, he said.

"Jasuben's son went to check on them around 8 am and found them lying unconscious and informed the police. The victims had vomited. Samples from the scene were sent for examination, and the bodies have been sent for postmortem," Barot said.

While the exact cause of death was yet to be ascertained, there is a possibility that the victims died due to asphyxiation as a gas-powered geyser was running, he said.

Barot said the possibility of suicide appeared slim, but the police were investigating all angles.

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