A swarm of earthquakes was recorded Tuesday off Alaska’s Aleutian Islands, including the largest with a magnitude of 6.8 followed by aftershocks.

There were few reports of the underwater quakes in the North Pacific being felt in nearby communities in a sparsely populated region of Alaska and no reports of damage, officials said.

Natalia Ruppert, a seismologist at the Alaska Earthquake Center, said it was a “very unusual, very energetic swarm of earthquakes.”

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The largest quake, at magnitude 6.8, was preceded just minutes before by a couple of foreshocks. The strong quake occurred about 2:36 a.m., about 40 miles (64 kilometers) southeast of Nikolski, a community of 39 residents on Alaska’s Unmak Island. The community is about 900 miles (1,448 kilometers) southwest of Anchorage, the state’s largest city.

About an hour later, a magnitude 6.6 aftershock was reported in the same area, followed throughout the morning by about a dozen aftershocks with many magnitude 4.0 or higher.

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State emergency officials checked in with both Nikolski and Unalaska, home to Dutch Harbor, one of the nation’s busiest commercial fishing ports, after both larger quakes, said Jeremy Zidek, a spokesperson for the Alaska Division of Homeland Security and Emergency Management.

Neither community reported any damage, and in fact those in Unalaska — which is located about 110 miles (177 kilometers) northeast of the epicenter — didn’t feel either, he said.

This area of the Aleutians, a chain of islands that jut off from southwest Alaska, has experienced a lot of seismic activity in the last year, including several large earthquakes, Zidek said.

None has produced any major damage or a tsunami, he said.

“We don’t want people to become complacent just because there’s been strong earthquakes and they didn’t generate tsunamis,” Zidek said. “That doesn’t mean that the next strong earthquake won’t.”

He cautioned if a community activates a tsunami warning siren or if a quake produces violent shaking for 20 seconds or more and you’re near a coastal area, “it’s time to head for higher ground.”