FBI agents armed with a search warrant on Tuesday questioned employees at the offices of Krahl Construction for several hours, a bureau spokesman confirmed.
Chicago FBI spokesman Ross Rice said the employees were questioned as part of an "ongoing criminal investigation," and confirms only that agents were "looking for evidence of a crime."
Krahl voluntarily shut its office, at 322 S. Green St., on Tuesday. Employees were ordered into a conference room initially so that agents could work without fear that an employee would try to hide or shred evidence, according to a source.
Representatives from Krahl did not return repeated calls for comment.
Krahl is a more than $100 million-per-year commercial construction company specializing in interior construction for office buildings and health care companies.
One of its biggest current projects is an old RR Donnelly building at 350 E. Cermak Rd., according to a source familiar with Krahl's business. That location, near McCormick Place, is being converted to a data center.
No charges were filed Tuesday.
Krahl Construction has an A+ rating with the Chicago Better Business Bureau.