Safety Insurance Group Inc. reported second quarter profits of $15.1 million, up slightly from a $15 million profit a year ago.

Year-to-date profits at the Boston-based insurer stand at $27.9 million, up 3.7 percent from 2009 levels.

The company said net written premiums for the second quarter increased by $12.6 million, to $153.6 million, on the strength of increased automobile and homeowner policies.

Safety also said yesterday its board of directors has authorized the repurchase of an additional $30 million in the company’s outstanding shares, on top of an existing $60 million share repurchase program. Such maneuvers are typically meant to boost a firm’s stock price.

Safety shares opened the trading day at $40.23; the company’s stock dipped as low as $34 per share in February.