The U.S. Coast Guard spent hours Thursday searching the waters off Louisiana for four people on board a helicopter that crashed while departing an oil platform.

The helicopter’s pilot and three oil workers went into the Gulf of Mexico about 8:40 a.m. CST, said Petty Officer Jose Hernandez, a spokesperson for the Coast Guard’s 8th District headquartered in New Orleans. Crews in a boat and a helicopter had found no sign of them by evening.

“So far we’ve only found debris and no people,” Hernandez said.

He said Coast Guard officials were still deciding whether to keep searching after dark.

One of the missing workers is 36-year-old David Scarborough of Lizana, Mississippi, according to his wife. Lacy Scarborough told the Sun Herald newspaper that she is expecting a baby and that her husband recently got a job promotion.

She said her family was praying that her husband and the others would be rescued safely.

“He enjoyed his job and his co-workers,” Lacy Scarborough said.

The helicopter went down about 10 miles (16 kilometers) offshore of Southwest Pass, a shipping channel at the mouth of the Mississippi River southeast of New Orleans. Helicopters routinely transport workers to and from oil platforms in the Gulf.

Hernandez said the oil platform is operated by Houston-based Walter Oil and Gas. The Associated Press reached out to a spokesperson for the company, who was not immediately available for comment.

Weather didn’t appear to be a factor in the crash, Hernandez said, as there were no reports of storms in the area Thursday.

The National Transportation Safety Board said it is investigating the crash.

Two weeks ago, the Coast Guard rescued three people after a helicopter crashed off the Louisiana coast while attempting to land on an oil rig platform. That crash occurred Dec. 15 south of Terrebonne Bay, roughly 60 miles (97 kilometers) west of the area the Coast Guard was searching Thursday.