St. John the Baptist Parish officials say boats, helicopters and high-water vehicles are searching for anyone in flooded parts of LaPlace, where water is continuing to rise.
They say anyone who needs rescue should get out where rescuers can see them.
They're also asking people to provide information about addresses, locations and names of people who need rescue in the parish.
St. John remains under a tropical storm warning with 25- to 35-mph winds. Tides will remain at 5 to 8 feet before receding slowly Thursday.
Louisiana State Police, National Guard, Wildlife and Fisheries agents, and St. John Sheriff and Fire personnel are continuing search and rescue throughout the day.