Aftershocks rattle Japan as death toll rises after powerful earthquake

At least 55 people had been confirmed dead after a massive earthquake and dozens of aftershocks struck Japan’s western coast, according to The Associated Press.

An earthquake with a preliminary magnitude of 7.5 struck at about 4:10 p.m. local time on Monday, with its epicenter on the Noto Peninsula, along the Sea of Japan, according to U.S. Geological Survey data.

More than 1,000 first responders had arrived in the region by Tuesday to help local police, fire and coast guard units, Prime Minister Fumio Kishida said. More than 2,000 firefighters were working in the region, he said.

"An inspection from above via helicopter has shown widespread damage including roads cut off, landslides and fires," Kishida said during a press conference.

A major tsunami warning issued on Monday near the epicenter was downgraded hours after the earthquake.

That and other warnings for Japan's western coast were lowered overnight to tsunami forecasts, with "slight" sea level changes expected, according to the agency.

"Now that the tsunami warning has been lifted, we will be able to secure sea transport routes, and we have been working continuously since last night to mobilize not only land transport but also air and sea transport to get the necessary supplies and rescue personnel to the area," Kishida said.

As of 9 a.m. on Tuesday, about 17 hours after the initial quake, the Japan Meteorological Agency had recorded an additional 147 earthquakes with a magnitude of 1 or higher near the epicenter, the agency said in a statement. Most of those were weaker quakes, with 118 under a magnitude of 3, officials said.

An earthquake with a preliminary magnitude of 5.6 was recorded on the Noto Peninsula at about 10:17 a.m. on Tuesday, the Cabinet Office, which is responsible for disaster management, said on social media.

Hayashi Yoshimasa, the chief cabinet secretary, on Monday afternoon warned that the threat of further earthquakes or tsunamis hadn’t subsided.

“Those people who are living in the area close to the epicenter, please pay attention to the information from the media and act on it,” Yoshimasa said in during a press conference.

ABC News' Ellie Kaufman and Joe Simonetti contributed to this story.