The Philippine Coast Guard has slammed China's Coast Guard for obstructing an investigation into suspected dynamite fishing near Pag-asa Island. The PCG, the Philippine Navy and the PNP Maritime Group responded to reports of foreign vessels blasting fish in the area on Sunday. The joint team ran into reported interference from Chinese Coast Guard units as it tried to verify the tip-off. Philippine officials say the obstruction stopped them from assessing the suspected blast fishing firsthand. Pag-asa lies in disputed waters where standoffs between the two coast guards have become routine. Manila has complained before about Chinese vessels blocking lawful operations near the island. Blast fishing wrecks coral reefs that support fish stocks and coastal livelihoods. The Coast Guard's pointed statement leaves little doubt about how seriously Manila takes the episode.