MITSERO, Cyprus (AP) — Cypriot authorities say poor visibility in a man-made lake’s toxic waters is hampering the search for a victim of a suspected serial killer.

Investigators believe a suitcase at the bottom of the lake contains the remains of one of seven foreign women and girls that a Cypriot army captain has confessed to killing.

Fire chief Marcos Trangolas told The Associated Press on Monday that it’s slow going for a robotic camera being used in the search. He said a sonar device will also be deployed.

The 35-year-old suspect said he put the bodies of three of his victims — a mother and daughter, and another woman — in suitcases and dumped them in the lake.

A suitcase containing the remains of an adult woman was retrieved from the lake Sunday.

FILE – Members of Cyprus Special Disaster Response Unit search for a suitcase in a man-made lake, near the village of Mitsero outside of the capital Nicosia, Cyprus, Monday April 29, 2019. (AP Photo/Petros Karadjias)

A diver, left, and an Investigator remove a suitcase found in a man-made lake, near the village of Mitsero outside of the capital Nicosia, Cyprus, Sunday, April 28, 2019. A travel suitcase containing the decomposing remains of an adult woman and a concrete block was retrieved from the bottom of a man-made lake, the chief of Cyprus’ Criminal Investigation Department said Sunday. The woman is believed to be one of the victims of a Cypriot military officer who has confessed to killing seven foreign women and girls. (AP Photo/Petros Karadjias)