Prosecutors launched a pre-trial investigation into the disclosure of the identity of an Interior Ministry operative, Prosecutor-General Boris Velchev told reporters on May 14 2008 on his way to the weekly session of the Supreme Judicial Council, as quoted by Dnevnik daily.

The probe is based on the findings of a report on the work of the ministry, carried out by the State Agency for National Security (SANS), he added, but declined to say whether the investigation targeted former interior minister Roumen Petkov. The probe was "against an unknown perpetrator", he said.

“If there is a need for Parliament to lift the immunity of a certain MP so that I can charge him, I would not hesitate to ask for that,” Velchev said. After Petkov reigned from office at end-April, he went back to Parliament as an MP.

The same day, Petkov told private Darik radio that he was ready to give up his immunity if it was necessary.   

As the Sofia Echo reported on April 4 2008 Velchev asked SANS to probe several cases of information leaks from the ministry.

The first happened on March 21, when Bulgarian media received anonymous records of phone calls where Ivan Ivanov, deputy head of the ministry’s chief directorate for combating organised crime (CDCOC), discussed ongoing investigations. The records were part of the ministry’s investigation into Ivanov, who was arrested on March 18.

SANS was also asked to investigate Iliya Iliev, former chief secretary of the ministry, who was arrested on March 25 and accused of taking a CD with classified information when he resigned in December.

The third case was the disclosure of the fact that controversial businessman Alexei Petrov was a secret agent of the ministry, which is the instance that could lead to Petkov's indictment.

Petrov's name surfaced in the media after former CDCOC head Vanyo Tanov told Parliament that Petrov had arranged a meeting between former interior minister Roumen Petkov and controversial businessmen Plamen Galev and Angel Hristov in 2006.

Tanov said that at the time of the meeting, Galev and Hristov were the targets of a police investigation. Petkov later confirmed Tanov’s words, but accused him of blowing Alexei Petrov’s cover as a secret collaborator of the ministry.

All these accusations led to Petkov's resignation.