RIGA - Latvian Prime Minister Aigars Kalvitis plans to meet with the head of the Latvian National Border Guard, Gunars Dabolins, to find out why the convicts that escaped the Riga Central Prison were not detained on the Latvian-Lithuanian border. Four prisoners escaped the Riga Central Prison on the night of Aug. 9. They were detained on the Lithuanian-Polish border on Aug. 11.As the Baltic countries attempt to meet Schengen Treaty requirements, Kalvits wants to know why border guards did not detain the prisoners before they fled into Lithuania.The escaped prisoners, aged between 21 and 33 years, were convicted for serious crimes such as murder, robbery and rape. Dabolins told the Baltic News Service that the convicts were able to cross Latvia's border with Lithuania because the border was not properly guarded. While preparing to join the Schengen Treaty, Latvian border guard authorities have been focusing more on the EU's external borders, moving the staff who used to work on the border with Lithuania and Estonia to Latvia's Eastern border, Dabolins said.