Bulgaria is observing a day of national mourning on Wednesday 11 November for the victims of two serious pile-ups on the Trakia Motorway near Yambol. Eleven people were killed and 51 injured in the fog-bound crashes on 10 November, according to Radio Bulgaria. ## Flags at half-mast as country pays tribute National flags at government institutions are flying at half-mast, and all official celebrations and entertainment events have been cancelled. Prime Minister Rumen Radev has cancelled his participation in the United Nations COP31 climate conference in Antalya, Turkey. The government is expected to approve financial compensation for the families of those killed, the BTA news agency reported. President Iliana Iotova cut short her participation in the Paris Peace Forum and is returning to Bulgaria. ## Fog blamed for chain collisions The crashes happened near the Zimnitsa interchange on 10 November, when dense fog suddenly reduced visibility on the motorway. Police, firefighters and ambulance crews were sent to the scene, where cars and trucks were piled up across both sides of the road. Of the 51 injured, 18 are being treated in Sliven, eight in Yambol and seven in Burgas. Thirteen people remain in serious condition, and a Romanian citizen in hospital in Burgas is in the most critical condition. The motorway has reopened in both directions between the Zimnitsa and Kabile interchanges after 86 vehicles involved in the chain collision were removed, although the regional governor has warned that fog has returned to the area.