MOSCOW (AP) — One man was killed after a massive fire on Friday ravaged a shopping mall on Moscow’s northwestern outskirts.

Authorities said the blaze at the OBI store, part of the MEGA shopping mall in Khimki outside the Russian capital was sparked by welding that apparently violated safety regulations.

The huge blaze erupted before the mall opened it’s doors to customers, engulfing the entire building of 17,000 square meters (183,000 square feet).

Officials initially said arson may have been involved, but later said it was due to unsafe welding.

A probe into the possible violation of safety rules has been launched.