President Donald Trump may have fired State Department Inspector General Steve Linick because he was investigating U.S. military sales to Saudi Arabia, Democratic lawmakers said on Monday, although Secretary of State Mike Pompeo said he sought Linick’s removal because his work was undermining the department.

President Trump continued his purge of inspectors general late Friday, moving to oust Steve A. Linick, who had served in that post at the State Department since 2013, and replacing him with an ambassador with close ties to Vice President Mike Pence. The decision to remove Mr. Linick, first reported Friday night by Politico, is the latest in a purge of inspectors general whom Mr. Trump has deemed insufficiently loyal to his administration, upending the traditional independence of the internal watchdog agencies whose missions are to conduct oversight of the nation’s sprawling bureaucracy.