Initial reports suggested up to 60 were injured - with one man dead - reports have since said the figure is closer to 18.
Police have cordoned off the site and are asking people to avoid the area. Several fire brigades were called to fight the flames while rescue workers treated the injured.
The incident occurred at Gas Connect Austria's hub in Baumgarten shortly before 9 a.m. local time, according to a spokesman. "There are miles of thick, black clouds of smoke".
The situation is now under control, according to the fire service, and extinguishing is now under way. The facility's operator initially said all the casualties were Austrian, but later said the one with less severe injuries include employees of contractors from six other countries.More news: David Moyes: Adrian has the No 1 jersey at West Ham
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"If we had had the [Trans Adriatic Pipeline], we would not have to declare a state of emergency", Calenda said, referring to a planned pipeline that would carry gas from Azerbaijan through Greece and Albania to Italy. The facility was "shut down in a controlled state and is offline", the company said.
The shock waves of the blast have already been felt far beyond the boundaries of the station, which serves as a crucial hinge point between gas suppliers in Russian Federation and Norway and pipelines sending that gas on to Italy, the United Kingdom and other European countries. He added that gas supplies in Slovakia had not been affected.
The explosion was at one of Europe's main hubs. Natural gas from Russia, Norway and other countries is taken over there, measured, tested and compressed for onward transport.