Cairo | An oil-drilling ship capsized in the Gulf of Suez, killing at least four crewmen and leaving four others missing, authorities said Wednesday.

The drilling ship overturned Tuesday evening off the city of Ras Ghareb, on the African side of the Gulf of Suez, the Red Sea's northwestern arm and a crucial shipping route, the Petroleum Ministry said in a statement.

There were 30 workers on board when the drilling ship capsized, said Amr Hanafy, governor of the Red Sea province.

Rescue teams recovered four bodies and rescued two 22 others who were taken to hospitals, he said.

He said ships from the Egyptian navy joined the search-and-rescue efforts which were still ongoing overnight for four missing crewmen.

It wasn't immediately clear what caused the drilling ship to capsize and authorities say investigations were ongoing. Local media reported it was being tugged for excavations in another area when it overturned.

The capsizing happened in an area called Gabel el-Zeit, a prominent Egyptian oil production site around 300 kilometres south of the Suez Canal, the ministry said in a statement.

The capsizing didn't disrupt vessels transiting through the canal, which links the Gulf of Suez to the Mediterranean Sea, Adm. Ossam Rabei, head of the canal authority, said.

Rabei said in a statement that 33 vessels were scheduled to transit Wednesday through the global waterway.