They were the lucky ones. An hour later, the real disaster struck.
Hundreds of shoppers and store employees, quickly ushered by staff to evacuate, watched on in horror as an explosion ripped through the building, exposing the structure's steel beams and catapulting debris across the parking lot.
First responders, initially fearful of entering the wreckage, hauled eight people from the partially collapsed site early on Wednesday, among them three dead. The status of four store workers remains unknown, mall operator Aeon said, adding that it was investigating a possible gas leak.
"I thought a bomb had gone off," Takateru Sonoda, 41, who runs a combined hair salon and cafe near the mall, told news agency Jiji Press.
"There were people calling on others to evacuate and sirens were ringing out. Nearby roads were gridlocked, it was a state of panic," Sonoda said.
Japanese Prime Minister Sanae Takaichi said on Wednesday it was a "race against time" to rescue those still trapped in the mall and others affected by the quake. Around 170 soldiers have been deployed to help with rescue operations at the site.
MALL TOUTED SAFETY FEATURES
The mall, the biggest in the prefecture, had just reopened last month as a new and improved shopping and entertainment complex to commemorate its recovery from another deadly tremor a decade ago.
After being badly damaged in the magnitude 7.3 Kumamoto earthquake in April 2016, the operator highlighted its seismically reinforced ceilings and overall improvements to safety and resilience as part of its redevelopment.
Still, one worker manning one of the mall's 200 stores told the Yomiuri newspaper that Tuesday's temblor shook the building for 10 seconds and brought him to his knees.
Another 22-year-old employee at the mall's cinema told the newspaper that the quake threw up a disorientating cloud of dust.
Despite the chaos, staff promptly followed protocol to evacuate more than 200 shoppers and workers to a car park where many took shelter in their vehicles in sweltering summer heat, the workers said.
Some people, however, went back into the building prior to the explosion, Kyodo news agency reported, citing customers.
Kazuya Tsurunaga was stunned by the blast while cleaning up dishes and glasses broken by the earlier earthquake inside a pub about 300 metres (328 yards) from the mall.
"A large cloud of smoke was billowing up, and because the wind happened to be blowing, and the wind direction was toward the shop, it was like volcanic ash was falling around us," he told broadcaster TBS.
For the first few hours after the blast, police officers and firefighters could not enter the wreckage because of the risk of further building collapse amid a series of aftershocks, a police official said. By the end of Tuesday, more than 100 aftershocks had occurred in Kumamoto.
GAS WARNINGS
Video footage shot by a police officer who braved the wreckage early on Wednesday showed large sections of the ceiling had collapsed, store fronts had been blown open and furniture was strewn across the floor.
Some rescue workers reported smelling gas, Japan's government spokesperson Minoru Kihara told a press conference on Wednesday. A TV correspondent reporting from the site said an emergency vehicle repeatedly urged people not to get near the mall due to a possible gas leak.
Kihara said the mall used LPG (liquefied petroleum gas), which is transported in large canisters rather than via a pipeline.
Piped gas is automatically shut off by network operators if seismic activity reaches a certain threshold or damage is confirmed to the line, a spokesperson for the Japan Gas Association said.
But LPG also has such safety protocols, an official with the Japan LPG sales association said. Microcomputer-controlled meters automatically shut off supply if they detect abnormalities such as leaks or pressure fluctuations, and are designed to cut supply during seismic activity of intensity 5 or higher, the official said.
Gas suppliers and safety service providers can also remotely shut off supply via radio transmission in emergencies, he added.
Aeon declined to comment on its gas supplier or gas safety protocols.
"We would like to express our deepest condolences to those who lost their lives," the firm said. "We also extend our sincere apologies to the bereaved families and to those who were injured."
(Reporting by Anton Bridge, Satoshi Sugiyama and Yuka Obayashi in Tokyo; Joseph Campbell and Tim Kelly in Kumamoto; Editing by Stephen Coates)
