OUAGADOUGOU, BURKINA FASO — Burkina Faso's President, Blaise Compaore, who executed his two most senior government ministers for attempting to overthrow him Monday, has ordered an investigation into the plot. At least two other people have been arrested. The plot was said to have been led by the Defense and Economic Promotion Ministers Jean-Baptiste Lingani and Henri Zongo. They sought to arrest Mr. Compaore as he stepped off a plane returning from abroad. But the plan failed after soldiers refused to carry out the orders to detain Compaore.