Two classes at the Neunkirchen State Vocational School were evacuated on Wednesday morning due to an acid leak. The fire brigade was called out. When nitric acid was mixed with alcohol, a "foul-smelling cloud was created" and smoke developed, said police spokesman Johann Baumschlager. Seven students were slightly injured, two of whom were taken to hospital, said Sonja Kellner, spokeswoman for the Lower Austrian Red Cross.