The body of Faridah Hashim, 63, was found by her son-in-law at 2.30pm.

Southwest district police chief Supt AA Anbalagan said the woman was believed to have been murdered before being dumped into the 1.5-metre deep septic tank.

“The preliminary examination by the forensic team found a slash wound on her throat.

“Police also found a knife believed to be the murder weapon near the septic tank, and blood stains on the tank’s cover,” he said, adding that the police were tracking down the woman’s son to assist in the investigation.

Anbalagan said the unemployed man, believed to be a petrol-sniffing addict, had two previous records of causing hurt to his sister and was said to have often scolded the victim for not giving him money.

The body was taken to the Penang Hospital for post-mortem.