STOCKHOLM (Reuters) - The Swedish Radiation Safety Authority has issued a level 2 severity rating on a 7-degree scale for an incident on Sept. 21 at a nuclear testing facility in which radioactively contaminated material spread at the site.

Level 2 on the International Nuclear and Radiological Event Scale represents an “incident”. The 1986 Chernobyl and 2011 Fukushima disasters are level 7 on the INES scale.

The authority said the owner of the facility on Sweden’s east coast, nuclear services firm Studsvik Nuclear, had started to decontaminate, and the contamination was confined to the site.

No one was on site at the time of the incident, it said.

It said the spread took place in connection with a false fire alarm and resulted in considerable surface contamination. It did not describe the incident further.

Studsvik Nuclear Chief Executive Michael Mononen said radiation levels in the contaminated areas of the facility are very low.