evidence: Meanwhile, Chinese actions have also increasingly worried Indonesia. Indonesian territory extends to Natuna Island and an associated array of natural gas fields in the southwestern portion of the South China Sea. Chinese fishing boats have steadily encroached on its waters—much like they had on Scarborough Shoal. More alarming, one Chinese fishing boat detained by Indonesian authorities for illegal fishing has been seized back by the China Coast Guard. China’s growing naval capabilities have therefore also raised concerns. Most worrisome, Indonesian requests to clarify whether Natuna Island (and the surrounding waters) are encompassed within the nine-dash line have not received official clarification from Beijing. Instead, the PRC has said that, while it recognizes Indonesian sovereignty over Natuna island, it still retains "overlapping claims to maritime rights and interests." These issues led Indonesia to expand military facilities near Natuna in 2016. This has included expanding the island’s runway and increasing the number of troops deployed there. In 2017, Djakarta announced that it would rename the area near Natuna, within its own Exclusive Economic Zone, the North Natuna Sea. The Chinese promptly rejected this move, warning that it would not be "conducive" to good relations. The name change has been implicitly endorsed by the United States, however. Secretary of Defense James Mattis used the term while visiting Indonesia, saying, "We can help maintain maritime domain awareness in the South China Sea, the North Natuna Sea. . . . This is something that we look forward to doing."