By Daria Sito-Sucic

SARAJEVO (Reuters) -A fire at a retirement home in the city of Tuzla in northeastern Bosnia claimed a 12th victim on Thursday, after an 84-year-old woman succumbed to injuries, the Tuzla hospital said. 

The fire broke out on Tuesday evening on the seventh floor of the old building where the victims were accommodated. Ten people died during the night and 30 others were treated in the hospital, of whom two have since died. Out of 14 patients who were still being treated in the hospital, two were in a critical condition, the officials said.

Autopsy examinations showed that all the victims, six men and six women, died from suffocation after breathing carbon monoxide, the Tuzla prosecutor's office said in a statement.

An investigation was completed on Thursday but prosecutors were still waiting for reports from police, power and fire experts to determine the cause, the office said. 

A day of mourning for the dead in the Tuzla retirement home was declared in the Bosniak-Croat Federation, one of Bosnia's two autonomous entities, and in neighbouring Montenegro.

(Reporting by Daria Sito-Sucic; Editing by Alex Richardson)