At least three people were killed when a helicopter crashed in Nigeria while en route to an oil rig, state oil company NNPC said.

Contact with the East Winds Aviation helicopter was lost while it was flying from Port Harkur to the Oil Production Storage & Offloading (FPSO) platform, the NNPC said. It carried a total of eight people, six passengers and two crew members.

The search and rescue operation is ongoing and authorities are investigating the cause of the crash, company spokesman Olufemi Soneye said. Three bodies have been found so far.

According to the Ministry of Civil Aviation, the Sikorsky SK76 helicopter “dived into the sea near Boni Finima, in the Atlantic Ocean”. Military and other aircraft have been deployed to the area to help locate him and rescue any survivors, a ministry spokesman, Odutayo Olusegi, said.

Nigeria, Africa’s most populous country, has had a poor aviation safety record in the past, but in recent years the situation has improved.