The indices of the Bulgarian Stock Exchange closed mixed on Monday, as the blue-chip SOFIX index put an end to the string of losses it has suffered since the beginning of the year, bourse data showed.The SOFIX index, which tracks the 15 most traded and capitalised companies listed on the Sofia bourse, added 0.10% to 568.05 points, supported by gains in First Investment Bank (Fibank) and software developer Sirma Group Holding. The BGREIT index, which tracks real estate investment trusts listed on both the regulated market and the BaSE Alternative Market of the Sofia bourse, closed at 120.33 points, compared to 120.46 points on Friday.