The island’s coast guard said the incident is a national-security matter and possible case of Chinese sabotage.

This is the latest in a series of incidents in recent years in which undersea Taiwanese cables have been damaged — with Taipei in some instances blaming China. Earlier this year, a Chinese cargo ship was suspected of severing a link northeast of the island.

Taiwan’s coast guard detained a cargo ship and its Chinese crew on Tuesday and said it was investigating whether the vessel had deliberately cut an undersea telecoms cable in the latest possible breach of the island’s communication lines.