Police in Poland have launched a murder investigation after a mother and her two daughters died after being found inside a septic tank near their home. Unconfirmed local reports suggest the incident could have been a murder-suicide.

Emergency services were called to the scene in the village of Helenów Pierwszy, central Poland, by the husband and father of the deceased. He said his wife and daughters, aged 6 and 8, had disappeared and noticed “disturbing signs” near the septic tank, police said. Four fire crews and a diving unit were deployed for the rescue operation where three bodies were recovered.

The 32-year-old mother was pronounced dead at the scene.

Both children were rushed to hospital where they later died.

According to Polish newspaper Gazeta Wyborcza, sources familiar with the investigation says it seems the mother, who was receiving psychiatric treatment, intended to drown her daughters and then take her own life.

The report said the woman’s throat was slit and a suicide note was left.

These claims have not been confirmed by authorities.

Sylwia Lewandowska, spokeswoman for the District Prosecutor's Office in Konin, told Polish outlet Fakt: “These are purely speculations. The situation is very tragic, this is the initial stage of the investigation, and for now we cannot discuss any findings due to the victims' relatives.”

A neighbour claimed the deaths happened while the husband was collecting medication from the pharmacy.

They told Wirtualna Polska: "I can't believe what happened. I heard that this woman's husband went to the pharmacy to get some medicine because she sent him. And when he came back, everything was already there... The tragedy was over, you could say.”

The local prosecutor’s office said “there is a high probability that a crime has been committed”.

Autopsy and toxicology tests will be carried out on Thursday.

Police have said no scenario has been ruled out, with the investigation ongoing.