Coast Guard officials told Fox8 that pieces of the helicopter have been located but there is no sign of the people on it.
Coast Guard Petty Officer Jose Hernandez told WVUE that the crash took place after the pilot picked up three oil workers from a platform owned by Houston-based Walter Oil and Gas.
PO Hernandez told the Associated Press that the weather did not appear to have been an issue in the area.
The Coast Guard called off its search at around 5pm on Thursday, and family members were told that the oil company will conduct its own recovery operation first thing on Friday morning, according to WLOX.
One of the workers on the helicopter was a Mississippi man, 36-year-old David Scarborough, who is a relative of a WLOX employee, the news station reported.
His wife, Lacy Scarborough, told The Sun Herald newspaper that she is pregnant and that her husband had recently been promoted.
“He enjoyed his job and his co-workers,” Ms Scarborough said.
Earlier this month, the Coast Guard rescued three people after a helicopter crashed off the Louisiana coast as it tried to land on an oil rig platform south of Terrebonne Bay.