A 7.4 magnitude earthquake, followed by several strong aftershocks struck off the coast of Taiwan on Wednesday morning, killing seven people and injuring at least 736, according to Taiwan’s fire department.

This is  Taiwan’s biggest earthquake in at least 25 years . According to the authorities, 77 people are reportedly trapped in tunnels and collapsed buildings as rescuers used ladders to help some people descend to safety.

The powerful 7.4 magnitude tremor shook the island’s east coast, hitting at 7:58 a.m. local time 18 kilometers (11 miles) south of Hualien city and at a depth of 34.8 kilometers (21 miles), according to the US Geological Survey. It was followed by several strong aftershocks with tremors felt across the island.

Taiwan’s National Fire Agency (NFA) said the severity of the injuries remains unclear.

“It was very strong. It felt as if the house was going to topple,” said Chang Yu-lin, 60, a worker in a hospital in Taipei, the capital.

All the deaths were in Hualien County, among them three hikers killed by falling rocks in the tourist hotspot Taroko Gorge, the NFA said. Falling rocks also killed a truck driver in front of a tunnel on the east coast’s Suhua Highway, it added.

The quake hit at a depth of 15.5 km (9.6 miles), just as people were headed for work and school, setting off a tsunami warning for southern Japan and the Philippines that was later lifted.

Video showed rescuers using ladders to help trapped people out of windows, while elsewhere there were massive landslides, as strong tremors in Taipei forced the subway system to close briefly, although most lines resumed service.

Chinese state media said the quake was felt in the south-eastern province of Fujian, while a Reuters witness said it was also felt in the commercial hub of Shanghai.

In Taiwan, military personnel were dispatched to help with disaster relief and schools and workplaces suspended operations as aftershocks hit the island, according to the Defense Ministry.

Taiwan’s outgoing President Tsai Ing-wen said Wednesday she had ordered her administration to immediately get  on top of the situation and understand local impacts as soon as possible.

Tsai also told the administration to provide necessary assistance, and work together with local governments to minimize the impact of the disaster.

Taiwan, a self-ruled island east of mainland China, is home to about 23 million people, most of whom live in the industrialized cities of its west coast, including the capital.