Grant Thornton LLP, one of the larger accounting firms outside of the Big Four, is under fire from regulators for the way it conducted audits of 15 publicly traded companies.

The findings, contained in inspection reports released Thursday by the Public Company Accounting Oversight Board, were similar to criticisms raised in separate reports the board issued last year on the four biggest accounting firms, PricewaterhouseCoopers LLP, Ernst & Young LLP, KPMG International and Deloitte Touche Tohmatsu.