A scheduled execution in Tennessee was halted Wednesday night after Christa Pike remained alive despite receiving two doses of lethal-injection drugs, according to information released Thursday. Pike’s attorneys said she was in critical condition. Pike is on death row for the 1995 murder of Colleen Slemmer, who was 19. The execution was scheduled for Wednesday, Sept. 30, at Riverbend Maximum Security Institution in Nashville. The available details do not explain why the first dose failed to kill Pike, what prompted officials to administer a second dose, or what steps the state plans to take next. Those unanswered questions put Tennessee’s execution procedures under scrutiny and renew concerns about the risks and oversight involved when the government carries out a death sentence. The incident also leaves Pike’s legal and medical status uncertain. Her attorneys’ account that she was in critical condition was the latest information available Thursday.