Chief Prosecutor Sotir Tsatsarov said indictments against two named suspects have been delayed by the discovery of a third suspect, the Sofia News Agency reported Thursday.
"This does not mean the indictment will be postponed indefinitely, but we'll need a bit more time. We will have a lot more evidence." Tsatarov was quoted as saying."
Tsatsarov said in September the investigation would be completed by March 2014.
The July 2012 bus bombing in the parking lot of Burgas' Sarafovo airport killed five Israeli tourists, the Bulgarian bus driver and a suspected suicide bomber, the Sofia News Agency said.
Thirty-five people were injured.