The British-Swedish pharmaceutical company said increased pressure in a tank in the factory meant that there was a risk of isopropylamine – a colourless flammable liquid which burns and can cause skin and eye irritation as well as difficulties breathing and unconsciousness – leaking out.
“It is dangerous,” an emergency services spokesperson told Swedish newswire TT. The fire and rescue services dispatched firefighters from four different stations as a precautionary measure.
Around 1,500 employees were escorted out of the building after the risk was detected.
Staff eating pizza and waiting to be allowed back inside the building. Photo: Erik Simander/TT
Earlier in the day a blackout knocked out power in large parts of southern Stockholm county, including Nynäshamn, Ekerö and the entire town of Södertälje, where AstraZeneca's factory is located.
AstraZeneca spokesperson Jacob Lund told The Local the problem was caused by the pressure failing in one of its cooling systems as a result of the power cut. The back-up system did not immediately kick in and when the temperature started rising the decision was made to evacuate the building.
“Then power came back on fairly soon after the incident and the cooling system started working again,” he said. “Now we're getting the levels back down to normal and until then the staff will have to stay outside in the summer warmth so that they can be completely safe when they return.”
“I would not say there was any grave danger. But we made proactive decisions, evacuated the staff and called the emergency services to be on the safe side.”
AstraZeneca staff playing summer games in the park after the evacuation. Photo: Erik Simander/TT
The power outage is understood to have been caused by a faulty transformator owned by electricity network operator Vattenfall. Around 8,000 households on Ekerö and 4,500 in Nynäshamn were also affected, as well as trains between Södertälje and Stockholm. Rail traffic resumed at around 11.30am.
Reporting by Emma Löfgren and Joel Forslin