A data center in Tokyo was the site of a fatal fire, killing five and injuring 50. The data center is believed to belong to Amazon, as the latest AWS facility in the region.

The building, which is located in the Tokyo suburb of Tama, caught fire at 1:45 PM on July 26, and continued to burn for eight hours before it could be put out.

The building management company, Mitsui Fusodan, said that the name of the building owner could not be revealed due to confidentiality restrictions; but ‘several industry stakeholders’ told Japanese news outlet Nikkei that the data center belonged to Amazon Web Services.

Construction of the facility, known as the Tama Technology Building, began last summer and was expected to be completed in October. The building is comprised of seven levels, three above and four below ground.

There were approximately 300 construction workers on site when the fire broke out. It is believed that the fire originated on the third basement level, where steel beams were being cut with a torch. Sparks from the torch may have reached insulation materials, starting the fire.

Four men died in the basement, and one was found on the third floor. Approximately 50 additional workers were treated for fire-related injuries, 22 in serious condition, according to the Tokyo fire department. Police believe there may still be one person on site, in one of the basement floors.

The eight-hour blaze damaged about 1/3 of the building. Amazon was contacted by Japanese and U.S. news outlets, but has yet to confirm ownership of the building or make a statement regarding the fire.

AWS launched the Tokyo region in 2011, the second in Asia Pacific following Singapore. Currently, the company maintains four availability zones in Tokyo, the highest number following the company’s core data center concentration in Northern Virginia.

Amazon’s cloud arm has been highly successful in Japan, with the number of AWS customers in Japan increasing by 500% from 2013-2017. This is largely due to cloud adoption in the Japanese financial sector, and Amazon’s partnership with Sony.