HOUMA, La. (AP) — Federal investigators were set to begin probing today why a helicopter bound for an offshore oil platform crashed in Louisiana’s marshlands, killing eight and critically injuring another.

The helicopter, operated by PHI Inc., crashed shortly after taking off Sunday afternoon from the company’s base in Amelia, said Richard Rovinelli, a spokesman for the company. Two pilots and seven passengers were aboard when the plane went down about 100 miles southwest of New Orleans. The identities of the victims were not released.

Petty Officer Jaclyn Young said the lone survivor was transported to a medical facility in suburban New Orleans, and was in critical condition Sunday night. No update was immediately available this morning.

The National Transportation Safety Board was set to arrive today to begin investigating the crash, Rovinelli said.

Lafayette-based PHI is a primary provider of helicopter services to oil and gas platforms that dot the coast of Louisiana. It also flies medical helicopters.

Workers typically are flown to and from their worksites from coastal flight bases.

Young said the U.S. Coast Guard assisted Terrebonne Parish sheriff’s deputies in recovering the dead and rescuing the survivor from the marshy Bayou Penchant area. A sheriff’s office spokesman did not return a phone call seeking comment early this morning.

In June, a PHI Air Medical helicopter crashed in Texas, killing four. The accident in the Sam Houston National Forest killed the pilot, paramedic, nurse and a patient who was being transported from Huntsville to Houston.

That crew agreed to transport the patient after another helicopter company abandoned the mission, saying that cloud cover was too low, making visibility poor in the early morning darkness.