Taiwanese authorities said they had detained a cargo ship crewed by Chinese nationals, which investigators believe may have severed an undersea communications cable near the island on Tuesday. It was the latest in a series of murky incidents that have prompted theories that China and Russia may be turning to cable sabotage as a form of harassment at sea.

The cable that was damaged connected Taiwan to the Penghu Islands, which belong to Taiwan and lie about 30 miles west of the main island. Taiwan’s Coast Guard said that it was still investigating the latest incident and had not reached any conclusions about whether the severing was deliberate or accidental.