The Philippine navy is quietly reinforcing the hull and deck of a rusting ship it ran aground on a disputed South China Sea reef in 1999 to stop it from breaking apart, determined to hold the shoal as Beijing creates a string of man-made islands nearby.

Using wooden fishing boats and other small craft, the navy has run the gauntlet of the Chinese coast guard to move cement, steel, cabling and welding equipment to the BRP Sierra Madre since late last year, two navy officers who have been inside the vessel said in recent interviews.

The 100 meter-long (330-foot) tank landing ship was built for the U.S. Navy during World War II. It was eventually transferred to the Philippine navy, which deliberately grounded it on Second Thomas Shoal to mark Manila's claim to the reef in the Spratly archipelago of the South China Sea. A small contingent of Philippine soldiers are stationed onboard.