Chief Prosecutor Sotir Tsatsarov said the charges against the two individuals, whose identities were not released, will be filed in court by March.
"We know the countries where those two suspects are located. At present, we are conducting actions to identify their third accomplice," he told the Sofia News Agency.
In July, the Bulgarian Ministry of Interior released the identities of two suspects, Australian citizen Meliad Farah and Canadian citizen Hassan el-Haj Hassan.
It is not clear whether Farah and Hassan are the two suspects Bulgarian prosecutors are looking to extradite, the news agency said.
The men allegedly used false identities to register at Bulgarian hotels and later bombed a bus in July 2012, killing five Israeli tourists and their bus driver.
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