Police hunting for victims of a suspected serial killer stalking the Mediterranean island nation of Cyprus have pulled a suitcase containing the decomposing remains of a woman from the bottom of a toxic, man-made lake.

She is believed to be a victim of a Cypriot military officer who has confessed to killing seven foreign women and girls — including four Philippine nationals — in what is believed to be the country’s first serial killer case.

Cyprus’ Criminal Investigation Department chief, Senior Inspector Neophytos Shailos, said the suitcase was weighed down by a concrete block and contained a body in the advanced stages of decomposition.

He said investigators were working to determine the woman’s identity.

Greek Cypriot National Guard captain Nikos Metaxas confessed last Thursday to killing five women he met on dating sites, as well as two of their daughters aged six and eight, over a three-year period.

However, investigators say that figure is conservative and fear there may be as many as 30 victims.

Authorities have focused the search for bodies on Kokkinopezoula lake, 32km west of the capital Nicosia, after Metaxas told police he stuffed three of his victims into suitcases and tossed them into the water.

“After great and persistent effort and many difficulties, a travel case was pulled from the lake containing the body of a woman and a block of cement,” Insp Shailos said.

The unsettling hue of the lake, dubbed “red lake”, is due to high-level contamination from an abandoned copper pyrite mine nearby.

The case came to light on April 14 with the discovery of the bound body of 38-year-old Filipina Mary Rose Tiburcio down a flooded mineshaft near the lake.

That triggered a homicide investigation that led to Metaxas’ arrest before a second body — believed to be that of fellow Philippine national Arian Palanas Lozano, 28, was found in the same shaft on April 20.

Police said Metaxas has admitted to killing both women and suspect he also murdered Ms Tiburcio’s six-year-old daughter, Sierra, who remains missing.

Three other victims are thought to be 31-year-old Filipina Maricar Valtez Arquiola, who vanished in December 2017, and Romanian Florentina Bunea, 36, and her eight-year-old daughter, Elena Natalia, who have not been seen since September 2016.

Metaxas reportedly also led investigators to a military firing range where the decomposed remains of another woman were discovered down a pit.

Authorities say the body likely belongs to a seventh victim, a missing Nepalese woman called Ashita Khadka Bista.

Insp Shailos said a coroner who carried out a preliminary examination of the body inside the suitcase fished from the lake on Sunday determined it was an adult female.

It was one of two suitcases found in the lake on Saturday. Police divers have yet to retrieve the second and are scouring the water for a third.

Police have told reporters they tracked down Metaxas through computer messages found on a dating site used by Ms Tiburcio. Investigators said the pair dated for six months before mother and daughter vanished in May 2018.

A court heard on the night of their disappearance, Ms Tiburcio’s flatmate begged her not to take her six-year-old daughter to a prearranged date with the captain.

The flatmate said Metaxas had insisted Ms Tiburcio bring the girl so she could play with his two small children.

The case has terrified locals who have long feared a serial killer was preying on foreign women who came to the island for work.

Police Chief Zacharias Chrysostomou has ordered an internal probe to determine whether investigators had failed to properly investigate the women’s disappearances following accusations little was done to find them.

— With wires