As a search for a sailor believed to have fallen overboard from the guided-missile cruiser Stethem in the South China Sea enters its third day, two Chinese frigates have joined U.S. and Japanese ships combing thousands of square miles of ocean.
Navy officials with U.S. 7th Fleet confirmed to Military.com that two frigates from the People's Liberation Army (Navy) are assisting with the search.
The Chinese Defense Ministry has identified one of the frigates as the Liuzhou, according to an Associated Press report; the other has not been identified.
As of late Wednesday evening, the search had covered more than 11,000 square nautical miles, 7th Fleet spokesman Lt. Paul Newell told Military.com.
"Since this is an ongoing search, this number will only continue to increase," he said.
In addition to the Stethem, the dry cargo ship Amelia Earhart and offshore petroleum distribution ship Vice Adm. K. R. Wheeler, along with a P-3 Orion maritime patrol aircraft, have contributed to the search from the Navy, officials said.
Japan has also participated, sending two Japan Maritime Self-Defense Force ships: the helicopter carrier Izumo, with aerial search support from embarked helicopters, and the destroyer Sazanami.
The aid from China comes at a time of heightened tensions in the South China Sea, where China's territorial claims in the region are hotly disputed by the U.S. and neighbors in the region.
In early July, China said it dispatched ships and fighters to "warn off" the Stethem, which had been conducting a freedom-of-navigation operation, sailing within 12 nautical miles of the disputed island Triton in the South China Sea to protest Chinese territorial claims.
According to The Associated Press, the Chinese Defense Ministry said it was supporting the search for Stethem's missing sailor in a "spirit of humanitarianism."
The sailor went missing around 9 a.m. local time Tuesday, officials said. Stethem was conducting routine operations in the South China Sea at the time.