More than 30 Bulgarian customs officers working on a checkpoint on the brder with Turkey were arrested on suspicion of corruption on Thursday as the Balkan country attempts to clean up its borders and show it is fit to join the European Union's passport-free zone.
Bulgaria and its neighbour Romania, the European Union's newest and poorest member states, have to convince all members their governments and border controls meet required standards if they are to be included in the Schengen agreement, which allows passport-free travel between countries.
A failure to sever links between high-level officials and organised crime bosses has plagued the countries since the end of communism in 1989.
The arrested officials, eight of whom have already been indicted, were working at the Kapitan Andreevo checkpoint on the border with Turkey, which would become the southern frontier of the Schengen zone if Bulgaria was accepted.
The Interior Ministry said the arrests followed a three-month investigation.
"Our modest ambitions at the beginning were for about 10 people, but the 'catch' exceeded our expectations," Sofia City Prosecutor Nikolay Kokinov was quoted as saying by the local Focus news agency. " So far more than 30 have been detained."
Earlier this year, the Netherlands said Bulgaria and Romania had not done enough to gain the unanimous approval needed to be included in the Schengen zone.
The European Union has both countries under special monitoring for corruption. Romania has made some progress in addressing the problem in recent months, convicting several lawmakers and a former prime minister.
Political analyst Daniel Smilov said Bulgaria had not taken strong enough steps to deal with corruption in the past but that Thursday's arrests showed it was now making serious efforts.
"I see no reason why we shouldn't see senior officials convicted this time," he said.