A strong earthquake hit off of the South Pacific nation of Vanuatu on Sunday, but authorities said any threat of a tsunami had mostly passed, and there were no immediate reports of injuries or damage.

The magnitude-6.9 quake struck 50 miles north of the town of Port Olry and 253 miles north of Vanuatu's capital, Port Vila, according to the U.S. Geological Survey. It had a depth of 22 miles.

The Pacific Tsunami Warning Center initially said that "hazardous tsunami waves are possible" for coasts located within 186 miles of the quake's epicenter. But it said around 40 minutes later that the tsunami threat "has now mostly passed."

Vanuatu sits on the Ring of Fire, the arc of seismic faults around the Pacific Ocean where earthquakes are common. The nation is also prone to volcanoes and cyclones, and has been ranked by the United Nations University as the world's most at-risk nation for natural disasters.