Steward Healthcare is refusing to turn over to state officials its audited financial statements, setting off a behind-the-scenes tug of war that could lead to fines being assessed on the for-profit company. Steward, which is owned by the New York private equity firm Cerberus Capital Management, is notoriously tight-lipped about its finances. The only reliable source of information on the company's overall performance and its financial relationship with Cerberus has been its audited statements. For the past two years, Steward filed the statements with state regulators, who turned them over to CommonWealth in response to public records requests.