The latest news says that it was 60 passengers on the both buses.
The bus carrying school kids slowed down because of an accident and the other bus, carrying Corean tourist, crashed into the rear. A 24 meter tank truck managed to sverve off the road, nearly avoiding the two crashed buses.
33 passengers was sent to hospital by ambulance or by bus, 8 of them with serious injuries.
http://www.aftonbladet.se/nyheter/article16894389.ab (Tank truck on pic)