WASHINGTON — The agency in charge of workplace safety needs to do a better job of making sure employers keep accurate records on worker injuries and illnesses, congressional investigators said in a report released Monday.

The Occupational Safety and Health Administration is supposed to audit employer records in the most hazardous industries to keep tabs on accident and illness rates. But the Government Accountability Office report found inspectors often don't interview workers to verify what is in employer records.

The report said OSHA shouldn't rely solely on employer data because some companies pressure workers not to report injuries or illnesses.

In addition, about a third of health providers surveyed by GAO said they have been pressured to withhold medical treatment so a company could avoid filing an injury or illness report.

Part of the problem is that OSHA officials don't audit records until two years after incidents occur. That often means the workers involved in the incidents are no longer available to be interviewed.

Democrats on the House Education and Labor Committee ordered up the GAO report because they are skeptical of numbers that have shown the rate of workplace injuries and illnesses declining between 1992 and 2007.

The GAO did not determine that those numbers are flawed, but concluded that OSHA could get more accurate information if inspectors did a better job independently verifying the data employers provide.

In 2007, there were about 4 million cases in which workers were injured or became ill as a result of unsafe or unhealthy working conditions. OSHA inspects work sites in industries that typically have the highest number of workplace injuries, such as the transportation and chemical industries.

But the report also found that OSHA does not audit records in eight other "high hazard" industries — including amusement parks and ski facilities — because it has not updated agency regulations. The report urged OSHA to update its regulations to include those industries.

OSHA agreed with all the recommendations in the GAO report. Earlier this year, OSHA launched a new program that would increase the number of work sites audited to check the accuracy of injury and illness reports.