A cargo ship that ran aground off South Africa’s west coast during a severe storm last month has spilled oil after waves broke up the vessel.

The 125-meter (410-foot) MV Ultra Galaxy that beached at Brand se Baai northwest of Cape Town on July 9 has been pounded by heavy seas in recent days, causing the wreck to overturn, according to the South African Maritime Safety Authority. An aerial inspection identified oil in the surrounding waters and washing up on the nearby beach.

“It is too early to determine how much of the remaining oil has spilled from the wreck,” SAMSA said in a statement. About 170 people are involved in the cleanup operations.

Recent severe weather offshore South Africa’s east coast caused the CMA CGM Belem to lose 99 containers near Richards Bay, SAMSA said a separate statement on the weekend. A warning has been issued that it may not be safe for vessels to navigate through the area.