A fire broke out in a truck carrying paper on 23 June 2011. Thirty-four people were caught in the smoke-engulfed tunnel, of which twelve were sent to hospital. The cause of the incident was an escalated fire in the engine. The tunnel was thus closed for all traffic. As a temporary measure, two morning and two afternoon rush-hour free ferries were put into service between Drøbak and Sætre. The tunnel re-opened on 7 June, although vehicles with a weight exceeding 7.5 tonnes were not permitted to use it. Despite the regulation, the police caught several trucks and buses still using the tunnel.