In pictures: US power plant blast
**About five people remain unaccounted for after a huge explosion at a power plant in the US state of Connecticut, a fire official has said.**Middletown deputy fire marshal Al Santostefano said nearly 100 workers had been at the unfinished power plant on Sunday at the time of the explosion.
Five people were killed and at least 12 others injured by the explosion.
A damaged section of the plant was currently too unstable to be searched for survivors, Mr Santostefano said.
He said it was unclear whether those unaccounted for were missing in the accident or had made it away from the plant and not yet been contacted by authorities.
Officials are unsure how many people were at the plant because a number of different contractors had workers on the site.
But Mr Santostefano said interviews with survivors, contractors and labour union officials indicated there had been nearly 100 people at the facility.
Federal investigation
Officials said the blast had been at 1117 local time (1617 GMT) as workers were testing gas lines.
The Kleen Energy plant was due to open later this year. It is meant to provide electricity by burning gas.
State and federal inspectors are due to start an investigation into the explosion later on Monday.
People living up to 50km (30 miles) away said their homes had been shaken by the blast at the plant, being built south of Middletown, on the Connecticut River.
Some people said they had thought an earthquake had hit the region.
It took at least 100 firefighters an hour to contain the fire started by the explosion.