Democratic Sens. Bill Nelson of Florida and Jay Rockefeller IV of West Virginia have demanded numerous internal documents from Takata Corp. about its deadly air bag safety defect, saying a top executive at the Japanese manufacturer left them with “many significant questions” about the problem.

In a letter sent Monday to Takata chief executive officer Shigehisa Takada, the senators made 24 different requests for company papers and information on the problem to bring clarity that they said didn’t come last week from Hiroshi Shimizu, the manufacturer’s senior vice president for global quality assurance. At least five deaths have been tied to the defect, which prompted recalls of about 7.8 million U.S. cars and trucks in hot and humid climates, such as Southern states.