A 29-year-old mother in Hong Kong allegedly smothered her daughters to death with a pillow as she was having some relationship problems with her estranged husband.

The three girls, aged 2, 4 and 5, were found unresponsive in the same bed Monday and were eventually declared dead at a hospital.

"This is a very serious family violence case," Police Superintendent Alan Chung said, the South China Morning Post reported.

The unidentified mother and three girls were living in a subdivided apartment in Sham Shui Po. The woman moved into the apartment after she began suspecting her husband of having an affair, police said.

The accused, along with her three daughters, had met her mother and her younger brother for dinner Sunday, the night before the girls were found unresponsive.

The family felt the accused was speaking incoherently and was talking about ghosts, but they did not seek professional help for her at the time. The younger brother drove his sister and her three daughters back home the same night.

The woman called her mother Monday morning and told her her daughters were dead. When police arrived at the home, the bedroom was found locked. Cops broke the door open to find the three girls unconscious in bed. They were pronounced dead after being rushed to the hospital.

Investigators searched the bedroom and found blood on a couple of pillows, as well as on the bed and floor.

"Blood was found at the mouth and nose of one of the girls. We don't rule out that the three victims were smothered to death with the pillows. An autopsy will be carried out to ascertain the exact cause of the deaths," Chung said.

Police believe the murders may have stemmed from the couple's relationship problems. The couple had been separated for a year, AP News reported.

Chung also said it was possible the mother did not want others to have custody of her three daughters after a divorce between her husband and her.

The chief imam of Hong Kong, Muhammad Arshad, said the husband spoke to him about their marital issues several months before his daughters' deaths. The religious leader said the husband wanted to reconcile, but the woman did not want his daughters to see him because of his extramarital affairs.

"He sought reconciliation and to live with his daughters, because he loved his daughters very much. And she didn't want to give her daughters to her husband," said Arshad, the head of the Kowloon Mosque and Islamic Centre.

The woman was taken into custody, but it is unclear whether charges were filed against her.

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