Allstate Corp., the largest publicly traded U.S. car and home insurer, said Friday it will get a subpoena from the Department of Homeland Security for documents on homeowners’ claims arising from the 2005’s Hurricane Katrina. Allstate spokesman Mike Siemienas said the company was one of several participants in the federal flood insurance program that would get such a subpoena. He declined to comment further, saying Allstate had not yet received it.