More than 200 people remain unaccounted for and four people have been confirmed dead after the worst floods for decades hit the US state of Colorado, authorities say.

More than two months' of rain fell in less than two weeks, cutting off communities from power and clean water. More heavy rain was expected on Saturday across the state.

Search-and-rescue teams used boats and helicopters to pull stranded residents to safety and to try to find residents still missing.

Patrick Von Keyserling, an emergency official in Boulder County, an area heavily affected by flooding, said 218 people were unaccounted for.

"That number will fluctuate as families start locating people and as we pick up people that have been stranded with our helicopter operation," he told Al Jazeera. “We will continue throughout the day as long as the weather is permitting.

“Certainly the intent is to find all unaccountable people. Some may be at rescue centres or staying with relatives,” Von Keyserling said.

Power cut off

Two small farming communities in eastern Colorado were under evacuation orders as a surge from the flooding was headed in their direction on the plains, the Colorado Office of Emergency Management said on Twitter.

"The town of Orchard is in immediate danger. EVACUATE NOW," it said. "The town of Goodrich is under an evacuation order."

Motorists were trapped in their cars with emergency crews scrambling to reach them.  

“Many, many communities in our western mountains are completely isolated. There is no road access, no telephone information, no power, no water, no sewer”, said Sheriff Joe Pelle of Boulder County.

In Lyons County, many residents have had no access to clean water or power for two days. The area lies near the meeting point of two rivers, and days of flash floods have made it resemble an inland sea.

At least four people have been killed, including a couple swept away in floodwaters after stopping their car northwest of

Also killed was a resident whose body was found in a collapsed building near Jamestown, an evacuated enclave north of Boulder, and a man whose body was discovered during flood-watch patrols in Colorado Springs, about 160km to the south, officials said.

The floods are the worst to hit Colorado for more than 30 years, and have prompted President Barack Obama to approve a federal disaster assistance request.

Source: Al Jazeera and agencies