LAKE CHARLES, Aug. 27 (AFP) - At least four people were killed by Hurricane Laura in Louisiana and search teams may find more victims but the governor said on Thursday (Aug 27) that the most powerful storm to make landfall in the US state in living memory did not cause the "catastrophic" damage that had been feared.

"We have a lot to be thankful for," Louisiana Governor John Bel Edwards said at a press conference.

"It is clear that we did not sustain and suffer the absolute catastrophic damage that we thought was likely based on the forecast we had last night," Edwards said.

"But we have sustained a tremendous amount of damage," he said, and thousands of residents of the southern state have had their "lives turned upside down."

Hurricane Laura struck the coast of Louisiana early on Thursday as a Category 4 storm - the second-highest on the wind scale. It has since been downgraded to a tropical storm.

Hurricane Katrina, which left 1,800 people dead in 2005, was a Category 3 storm when it made landfall. Only one storm has made landfall in Louisiana with wind speeds as high as Laura - the Last Island hurricane of 1856, which left hundreds dead.

Edwards said the authorities have learned of four deaths, "all related to trees falling on residences."

"I'm concerned that as we continue to go out and do primary and secondary search and rescue we're going to find more fatalities," he said. "I hope not and pray not."

Edwards said there were about 600,000 power outages across the state and water services had also suffered some damage.

"We have a lot of work to do," he said.

Edwards said residents living near a chemical plant near Lake Charles where there was a chlorine gas fire had been told to shelter in place.