Raleigh, N.C. — A company that handled payroll and benefits administration for about 100 small and mid-sized firms in the Triangle has filed for bankruptcy.

The Castleton Group shut down unexpectedly on Dec. 18 as state federal authorities launched investigations into the company's finances. The state Department of Insurance determined the company's liabilities exceeded its assets by $6 million and that at least $8 million in payroll taxes were never paid to the Internal Revenue Service.

The closing left about 3,500 area workers liable for their own health and medical coverage.

Castleton's first hearing in bankruptcy court is scheduled for Jan. 28.