Nigerian authorities were putting emergency measures in place on Thursday to prevent an oil spill from a Royal Dutch Shell facility, the biggest leak in Nigeria for more than 13 years, washing up on its densely populated coast.

Tuesday’s spill, which Shell said happened while a tanker was loading oil, has led to the complete shutdown of the company’s 200,000 barrel per day (bpd) Bonga facility, about 120 kilometers off the coast of the West African nation.

Shell’s pipelines in Nigeria’s onshore Niger delta have spilled several times, which it usually blames on sabotage attacks and oil theft, though it did not in this case.

“It’s comparable to what happened in 1998 with the Exxon Mobil spill, in terms of the quantity that has been spilled, it’s the biggest since then,” Peter Idabor, director of Nigeria’s National Oil Spill Detection and Response Agency (NOSDRA), told Reuters by telephone from the capital Abuja.

In 1998, some 40,000 barrels leaked from a ruptured Mobil pipeline off the coast of Nigeria.