American Heather Mack holds her boyfriend Tommy Schaefer in a cell at Indonesian prosecutor office as the police handed her murder case to the prosecutor in Bali, Indonesia, Monday, Dec. 8, 2014. Mack and her boyfriend Tommy Schaefer are accused of murdering Sheila von Wiese-Mack, her mother, who was found stuffed inside a suitcase last August. (AP Photo/Firdia Lisnawati)

BALI, Indonesia - Indonesian police said Monday that they have completed their investigation into an American couple accused of battering the woman's mother to death and stuffing the body into a suitcase on the resort island of Bali.

State prosecutor Eddy Arta Wijaya said police formally handed over their investigation to prosecutors on Monday.

He said suspects Heather Mack, 19, and her boyfriend, Tommy Schaefer, 21, both from Chicago, were transferred to the custody of prosecutors in line with Indonesian criminal procedure. Prosecutors have 20 days to decide whether to formally charge the couple and bring the case to court. If they believe it is too weak, they can ask police for more evidence.

The badly beaten body of Sheila von Wiese-Mack, 62, was found inside the trunk of a taxi at the upscale St. Regis Bali Resort in August. Police say the couple had argued with her in the lobby of the hotel shortly before the killing, which is alleged to have taken place inside a room in the hotel.

Mack, who is six months' pregnant, and Schaefer have been held in separate cells.

On Monday, the couple met in a small cell at the prosecutors' office while waiting for the transfer process. They kissed and cuddled, and Schaefer stroked Mack's belly several times.

"My baby is a girl, she is fine," Mack told reporters from her cell. "I want her to stay in Bali so she can visit me anytime while I'm in jail."

Bali police Col. Djoko Hariutomo said officers had questioned 12 witnesses and their case included information from the FBI.

Officers brought the physical evidence to the prosecutors in large sacks, including the iron grip of a fruit bowl alleged to be the weapon used in the slaying and several computer hard drives containing hotel surveillance camera videos.

A Chicago-based attorney for Heather Mack, Michael Elkin, declined Monday to discuss the investigation. But Elkin said in a statement that Mack has told him that Indonesian authorities have treated her "with decency and in a humane manner."

Messages left Monday with Schaefer's American attorney, Thomas Durkin of Chicago, were not returned.

News from © The Associated Press, 2014