A couple in custody for allegedly holding a woman captive for nearly two months and abusing her so badly that she died are believed also to have killed and dismembered a second woman, German authorities said Tuesday.

The suspects are a 46-year-old man and his 47-year-old ex-wife, who still lives with him. Their names haven't been released because of German privacy laws.

The two have been under investigation since April 21, when they called an ambulance after their car broke down and rescuers found a woman inside suffering from head injuries and other abuse. The victim, identified only as a 41-year-old from Lower Saxony state, died shortly afterward in a hospital and doctors alerted authorities to the signs of abuse.

The woman, who had apparently answered an online personal ad, had been held in the couple's house outside the western town of Hoexter for nearly two months and had been made to sleep in an unheated room on a floor, prosecutors in nearby Bielefeld told reporters, the dpa news agency reported. An autopsy showed she suffered from blows to the head, among other injuries.

Once in custody, the female suspect told authorities she herself had been "massively abused" by her partner and confessed that she'd been involved in killing a 33-year-old in 2014, police murder commission head Ralf Oestermann said. After she was killed, that victim's body was cut up and stored in the freezer, and pieces were removed and burned in the couple's fireplace over time, he said.

The couple used the victim's phone to continue to send text messages to her mother, who only learned recently of her daughter's death after being contacted by authorities, police said.

The male suspect denies the allegations, Oestermann said.

Prosecutor Ralf Meyer said the motive is still not clear, but that it appeared to be more about power and control than sexual reasons.

Authorities said there is reason to believe that other women were abused, and already they have interviewed a woman from the Berlin area who recognized the house from photos on television and said she had also been injured by the couple.