Unconfirmed reports have suggested a Chinese nuclear submarine has crashed in the Taiwan Strait—the body of water that separates mainland China from Taiwan—days after Beijing launched military drills around the island in a “stern warning” to Taipei and Washington.

Reports circulating online have claimed that one of China’s Type 093, or “Shang-class,” nuclear submarines had crashed in unknown circumstances at some point in the past few days. Some of the reports claimed the entire crew onboard the vessel had been killed.

Beijing considers Taiwan a breakaway part of mainland China, to be eventually reunited under central control. But Taipei, which has established a democratic government, has long asserted its independence from Beijing and attempted to align itself with Western allies.

There has been no official confirmation of a Chinese submarine running into difficulty in the contentious strait, and experts have been hesitant to speculate. The topic was not mentioned in a press briefing