Federal officials to investigate Connecticut blast

BOSTON Feb 8 (Reuters) - Federal investigators headed to Connecticut on Monday to determine the cause of an explosion at an unfinished power plant that killed at least five workers and hospitalized dozens of others.

The U.S. Chemical Safety Board is sending seven officials to the privately-owned Kleen Energy Systems LLC plant in Middletown, which was in the final stages of construction when the blast occurred on Sunday.

Local authorities suspect a natural gas leak.

Investigators will examine what was happening at the time of the accident, including initial media reports that gas purging had occurred before the blast, said lead investigator Don Holstrom, who works out of the board's Denver office.

The agency is charged with investigating industrial chemical accidents.

Last week, it issued urgent recommendations that fuel gas codes be changed to improve safety when gas pipes are being purged, or cleared of air, during maintenance or installation.

Rescue workers returned with dogs on Monday as they continued to sift through the rubble at the plant, about 20 miles (32 km) south of the state capital Hartford, for possible survivors or further fatalities.

Between 50 and 200 contractors and subcontractors may have been at the site at the time of the blast, which was heard miles away and led to a brief, intense fire in one of the plant's largest buildings.

Al Santostefano, Middletown's deputy fire marshal, said one section of the plant was still too unstable to search.

Construction of the 620-megawatt duel-fuel power plant was 95 percent complete, and it was set to come on-line in the summer as one of New England's largest electricity producers.

Kleen Energy Systems is majority-owned by Energy Investors Funds Group, a private equity firm. The plant received a "power deal of the year" award from EuroMoney magazine in 2008 after EIF put together $1.35 billion in financing.

(Reporting by Ros Krasny; Editing by Paul Simao)