The Philippines said on Tuesday it had filed a fresh protest against China for allegedly harassing a Manila-registered archaeological ship in the Scarborough Shoal in the South China Sea, potentially prolonging a week-long maritime stand-off between the two countries.

The impasse was triggered by a Philippine navy ship’s attempt to detain eight Chinese fishing vessels for allegedly fishing illegally in Philippine waters last week. The Philippine navy vessel, the Chinese fishing boats and a Chinese maritime surveillance craft then left the shoal, easing the impasse somewhat.

But a Philippine Coast Guard ship and two Chinese maritime surveillance vessels are now involved in a further stand off, this time, over the research vessel, which is part of a joint project of the Philippine government’s National Museum and a French foundation to map the area for ancient shipwrecks.