Taiwan is investigating whether a China-linked ship was responsible for damaging one of the undersea cables connecting Taiwan to the Internet, the latest reminder of how vulnerable Taiwan’s critical infrastructure is to damage from China.

The incident happened at a time when anxiety was rising in Europe obvious sabotageincluding those directed at such underwater communication cables. Two optical cables under the Baltic Sea were discontinued in Novemberprompting officials from Sweden, Finland and Lithuania to stop a Chinese-flagged merchant ship in the area for weeks over possible involvement.

In Taiwan, communications were quickly rerouted after the damage was discovered and there was no major disruption. The island’s main telecommunications service provider, Chunghwa Telecom, was notified Friday morning that the cable, known as the Trans-Pacific Express Cable, had been damaged. That cable also connects to South Korea, Japan, China and the United States.

That afternoon, Taiwan’s coast guard intercepted the cargo ship near the northern city of Keelung, in an area near where six cables come down to land. The ship was owned by a Hong Kong company and was crewed by seven Chinese nationals, the Taiwan Coast Guard Administration said.

The damaged cable is one of more than a dozen that help keep Taiwan online. These fragile cables are vulnerable to breaking anchors that are dragged along the seabed by many ships in the busy waters around Taiwan.

Analysts and officials say that while it is difficult to prove whether the damage to these cables was intentional, such an act would fit China’s pattern of intimidation and psychological warfare aimed at weakening Taiwan’s defenses.

Taiwan said the cargo ship it intercepted was registered under the flags of Cameroon and Tanzania. “The possibility of a Chinese flag-of-convenience vessel engaging in gray zone harassment cannot be ruled out,” the Coast Guard said in a statement on Monday.

Such harassment, which inconveniences Taiwanese forces but does not lead to open conflict, has a desensitizing effect over time, according to Yisuo Tzeng, a researcher at the National Defense and Security Research Institute, a think tank funded by Taiwan’s defense ministry. That puts Taiwan at risk of being caught unprepared in the event of a real conflict, Mr. Tzeng said.

Taiwan experiences almost daily incursions by the People’s Liberation Army into its waters and airspace. Last month, China sent nearly 90 navy and coast guard vessels into waters in the area the largest such operation in nearly three decades.

China is also deployed militarized fishing boats and his coast guard fleet in disputes over the South China Sea region and stepped up patrols just miles off the coast of Taiwan’s outer islands, raising the risk of dangerous confrontations.

Such harassment has been “a defining feature of Chinese coercion against Taiwan for decades, but it’s really intensified in recent years,” said Gregory Poling, director of the Asia Maritime Transparency Initiative at the Center for Strategic and International Studies.

And in situations like this and the recent cable damage under the Baltic Sea, it is difficult for authorities to calibrate their response when the true identity of the ship is uncertain.

“Do you deploy a Coast Guard vessel every time there’s an illegal sand dredger or, in this case, a flag-of-convenience ship with Chinese connections that damages a submarine cable?” asked Mr. Poling.

Ship tracking data and vessel logs analyzed by The Times show the ship may have been broadcasting its positions under a false name.

Taiwan said the ship appeared to be using two sets of automatic identification system equipment, which is used to broadcast the ship’s position. On January 3, at the time Taiwan said the cable was damaged, a ship called the Shun Xing 39 was reporting its AIS positions in waters off the northeast coast of Taiwan.

About nine hours later, at around 16:51 local time, Shun Xing 39 stopped sending location data. That was shortly after Taiwan’s coast guard said it had located the ship and asked it to return to waters outside the port of Keelung to investigate.

A minute later, and 50 feet away, a vessel called the Xing Shun 39, which had not reported a position since late December, began transmitting a signal, according to William Conroy, a marine analyst at Semaphore Maritime Solutions in Wildwood, Mo., who analyzed the AIS data on Starboard ship tracking platform.

In the ship tracking database, both Xing Shun 39 and Shun Xing 39 are identified as cargo ships with Class A AIS transponders. Normally, a cargo ship equipped with this class of transponder would be large enough to require registration with the International Maritime Organization and obtaining a unique identification number known as an IMO number. Xing Shun 39 has an IMO number, but Shun Xing 39 does not appear in the IMO database. This suggests that “Xing Shun 39” is the true identity of the ship and “Shun Xing 39” is a fake, according to Mr. Conroy.

Taiwan’s coast guard publicly identified the vessel as the Shun Xing 39 and said the vessel was using two AIS systems.

Ship and corporate records show that Jie Yang Trading Ltd, a Hong Kong-based company, took ownership of the Xing Shun 39 in April 2024.

The waves were too big to board the cargo ship for further investigation, the Taiwan Coast Guard Administration said. Taiwan is seeking help from South Korea after the cargo ship’s crew said it was headed for the country, the administration said.

2023 the remote Matsu Islands, within sight of the Chinese coast, withstood unstable internet months after two undersea internet cables snapped. These fiber optic cables connecting Taiwan to the Internet suffered about 30 such outages between 2017 and 2023.

The frequent breakdowns are a reminder that Taiwan’s communications infrastructure must be able to withstand a crisis.

To ensure that Taiwan can stay online if the cables fail, the government has sought a backup, including building a network of low-Earth orbit satellites that can beam Internet to Earth from space. Most importantly, officials in Taiwan are racing to build their system without Elon Musk’s interferencewhose rocket company, SpaceX, dominates the satellite Internet industry, but whose deep business ties in China have left them wary.