Narragansett Bay Insurance Co. announced yesterday that three private firms have agreed to invest a total of $200 million in the company, a major influx of capital that will allow it to expand its homeowners business along the Eastern seaboard.

The additional money will enable NBIC to write perhaps 50,000 new homeowner policies, compared with its current portfolio of about 3,000, said Stewart H. “Nick” Steffey, chairman and chief executive officer. The company said it would expand its homeowners business with both coastal and inland properties.

And over the next four years, the company, which now has 27 employees, expects to hire another 100 workers as it grows, Steffey said.

“This is a very significant investment and recognition of the size of the market opportunity,” he said in an interview yesterday.

Among the investors is Pine Brook Partners LLC, a New York-based private equity firm cofounded in 2006 by Michael McMahon, a former Rhode Island economic development official.

The others are Soros Strategic Partners LP, which invests on behalf of George Soros and his family; and RenaissanceRe Holdings, a provider of reinsurance (insurance for insurance companies) to cover the risk of natural and man-made catastrophes.

NBIC, headquartered in Pawtucket, offers insurance to homeowners through a network of independent agents in Rhode Island, Massachusetts and New York. The company is a subsidiary of Blackstone Financial Group, the successor to the once-ailing Pawtucket Mutual Insurance Co. Blackstone acquired the former Pawtucket Mutual in December 2005 after it had been operating under state control for more than two years.

NBIC is hoping to fill the void left by several insurers who have left or curtailed coverage in the region following the Sept. 11 terrorist attacks in 2001, and Hurricane Katrina that struck the Gulf Coast in 2005. After those events, many insurance companies began to reevaluate the risks of insuring houses and businesses near the coasts. Some cut back on issuing policies, while others quit the areas altogether.

That left a big market opportunity for NBIC, Steffey said. In Rhode Island, Massachusetts and New York, homeowner insurance is a $6-billion market, he said.

But why would NBIC want to focus on an area that the insurance industry has pulled away from?

First of all, Steffey said, the reason other insurers left Rhode Island and other nearby states had more to do with balancing their risks by spreading policies across a wider geographic area.

They didn’t leave because it wasn’t profitable. In fact, Steffey said, New England has been more profitable than the national average.

For every $1 that customers in New England pay in policy premiums, only about 50 cents is paid out in claims, he said. Nationally, insurance companies pay out about 70 cents for every dollar received in premiums, Steffey said.

Why? Homes in New England tend to be better built, and New Englanders maintain their homes better, he said. And the national numbers have been skewed by hurricanes and earthquakes in other parts of the country.

Aside from profits, NBIC is expanding along the East Coast because company officials believe that it can better assess risks than some of its competitors, Steffey said.

NBIC customizes each homeowners’ policy to a specific house, he said. When a homeowner applies for a policy, the company inspects the house and notes the state of its electrical system, roof, heating system, and other parts that could have problems. In some cases, the company will not insure a homeowner unless some changes are made. For less serious issues, such as an aging roof or a loose railing on a stairway, the company will recommend it be fixed, and will sometimes lower a premium when the item is addressed.

The company will also determine how high the property is above sea level and storm surges, and use that data to help calculate the policy premium.

Since the policies are tailored to a particular house, the rate could end up being lower — or higher — than those of other insurance companies, Steffey said.

And finally, NBIC can better compete because it is focused on only homeowners insurance, he said. Companies that offer many types of insurance may be spreading themselves too thin in terms of gaining expertise and understanding risks in any particular market, Steffey said. “From our standpoint, there’s a real opportunity for specialists.”

He said NBIC will be looking to enter the insurance market in more states, including Connecticut and New Jersey. As it grows, he said, the companies will look for new business further south along the Atlantic coast.

“We’re still adolescents,” Steffey said. “We hope to work our way down the Eastern seaboard, in time, a little bit each year.”

tbarmann@projo.com