INSURANCE

Exstar Stock Plunges After Auditor Quits: Exstar Financial Corp.’s stock dived 29% after its auditing firm, Coopers & Lybrand, resigned in a dispute and withdrew its approval of Exstar’s 1993 financial statements. Exstar, a casualty insurer based in Solvang, Calif., saw its stock drop $2 a share Friday to close at $5 in Nasdaq trading. The dispute concerned Exstar’s treatment of $7.9 million in loans that the company made to TCO Insurance Services Inc., an affiliated underwriting manager. Exstar said Coopers & Lybrand changed its mind and decided that a portion of the loans should be treated as operating expenses, which would cause reductions in Exstar’s net income and stockholders equity for 1993 and the first two quarters of this year.