Divers have dragged a suitcase containing decomposing human remains from a toxic lake in Cyprus — the third such discovery in the east Mediterranean island nation's serial killer case.

Key points: Police said it was a "major development" in the unfolding serial killer investigation

Police said it was a "major development" in the unfolding serial killer investigation It is the third suitcase containing a body retrieved from the lake following a six-week search

It is the third suitcase containing a body retrieved from the lake following a six-week search A 35-year-old Cypriot army captain has confessed to the killings

Cyprus police spokesman Andreas Angelides said the discovery was a "major development" in the unfolding investigation of a Cypriot army captain who had confessed to the killing of seven foreign women and girls.

Mr Angelides said coroners examined the latest discovery at the scene while more specialised tests would be carried out to determine the person's identity.

"We proceeded with our search keeping two key factors in mind: the degree of difficulty and the level of danger involved," he said.

It is the third suitcase containing a body retrieved from the lake following a six-week search.

The 35-year-old suspect had told investigators he disposed of the bodies of a Filipino woman and a Romanian mother and daughter in the lake after placing their bodies in suitcases.

The body in the latest find is believed to be that of Maricar Valtez Arquiola, 31, from the Philippines.

The case came to light on April 14 when the bound body of 38-year-old Mary Rose Tiburcio, also from the Philippines, was discovered by chance down a flooded shaft near the toxic lake, part of a disused copper mine.

It is the third suitcase containing a body retrieved from the toxic lake. ( AP: Petros Karadjias )

The ensuing homicide investigation led to the captain's arrest following an assessment of his online communication with the victim.

A second woman's body — thought to be that of 28-year-old Arian Palanas Lozano, also from the Philippines — was found in the mineshaft a few days later.

Investigators said the suspect, who hasn't been named yet, confessed to the killings in a 10-page, handwritten note.

He led them to where he disposed of the bodies, including a dry well in a military firing range, where the remains of a woman thought to be Ashita Khadka Bista, from Nepal, were found.

The case put the spotlight on police failings in investigating missing person cases and led to the resignation of the justice minister and the firing of the police chief.

Officials said some later killings may have been prevented had "negligent" officers properly investigated the first missing person reports.

Police continue to search for the body of Ms Tiburcio's six year-old daughter in another lake after the suspect said he disposed of it there.

Authorities have spent six weeks searching the lake. ( AP: Petros Karadjias )

AP