STOCKHOLM (AP) — Sweden on Tuesday reported partial damage to an undersea telecommunications cable in the Baltic Sea running to Estonia that authorities believe occurred at the same time as damage to an undersea gas pipeline and telecom cable from Finland to Estonia.

Finland launched an investigation into possible sabotage after reporting the damage to its gas pipeline to Estonia last week.

Swedish Civil Defense Minister Carl-Oskar Bohlin said Tuesday that the damage to the cable between Sweden and Estonia appeared to have happened at the same time, but that it’s unclear what caused it.

“It is not a total cable break. There is a partial damage on this cable,” Bohlin said. “We cannot assess what caused the damage.”

Estonia’s economy ministry said the disruption in the Swedish-owned cable was in Estonian territory, about 50 kilometers (30 miles) off the island of Hiiumaa in northern Estonia, the Baltic News Service reported. Service was restored within a few days, the agency said.

Swedish Defense Minister Pål Jonson said his country’s police, military and coast guard were in contact with their Estonian counterparts regarding the matter. He said there also was heightened vigilance in the Baltic Sea.

“We see the issue of security for our critical infrastructure as a high priority, and take the current situation seriously,” Pål Jonson said at a news conference. He did not suggest who or what may have caused the damage.

Finnish and Estonian gas system operators on Sunday said they noted an unusual drop in pressure in the Balticconnector pipeline after which they shut down the gas flow.

The Finnish government on Tuesday said there was damage both to the gas pipeline and to a telecommunications cable between the two NATO countries.

On Friday, Swedish Prime Minister Ulf Kristersson spoke of a ”spaghetti of cables, wires” on the Baltic seabed which “is absolutely fundamental for data traffic.”

“We live in a time where civilian infrastructure is also very threatened in this security environment,” Kristersson said. “It is also a very clear lesson from Ukraine, i.e., attacking infrastructure that is for energy supply, food supply, water supply.”

The incidents come just over a year after the Nord Stream gas pipelines running between Germany and Russia in the Baltic Sea were damaged by explosions believed to be sabotage. The case remains unsolved.

A total of four leaks were discovered on Nord Stream 1 and 2 on Sept. 26 and 27 respectively. Two of the leaks were in the Swedish economic zone northeast of the Danish island of Bornholm, and two in the Danish economic zone southeast of Bornholm, and were outside national waters. Both Swedish and Danish seismic measurements showed that explosions took place a few hours before the leaks were discovered.

The blasts were deemed an act of sabotage by Sweden and Denmark.