MANILA (2nd UPDATE) – China could be trying to explore Benham Rise, Philippines' defense chief said, in what could be another source of conflict between the Asian neighbors.

Defense Secretary Delfin Lorenzana said on Thursday that satellite photos and incident reports indicate that China had sent a ship to Benham Rise.

“One of the survey ships is also plying the Benham Rise already. Last year, it was monitored for about three months,” Lorenzana said in a forum.

“We started to look at some of the -- we still have some friends who give us satellite photos, [and] these ships were actually plying the Benham Rise north of the Philippines [up] to Surigao.”

Lorenzana said he has given instructions to the Navy that if the survey ship returns, "accost them and drive them away."

The defense chief said the reason for the alleged Chinese survey in Benham Rise has yet to be determined, but that he has read a report saying the Chinese could be looking for a spot to place submarines.

Lorenzana also cited a report that a Chinese ship figured in an accident while plying Benham Rise in the Pacific Ocean, prompting the Chinese to bring one of its men to a hospital in Surigao City.

“What happened in December was… that survey ship had an accident inside the ship when they were somewhere there in central Philippines, at the Pacific Ocean. What the ship did was go to Surigao City and unloaded one patient and left,” he said.

Lorenzana made this revelation as the Philippines and China try to renew ties strained by the South China Sea dispute.

Since assuming presidency last year, President Rodrigo Duterte has sought closer ties with China, choosing to downplay the arbitral ruling on the South China Sea favoring the Philippines in exchange of reinvigorated economic ties.

The country's claim to Benham Rise, a 13-million-hectare area located east of Luzon island believed to be gas-rich, was approved by the United Nations in 2012.