Prime minister Rumen Radev has cancelled all his events in Varna and today's cabinet meeting after a serious crash on the Trakia motorway.
Many people were killed and injured. The injured were taken to hospitals in Sliven, Yambol and Burgas.
Emergency medical teams, teams from the Military Medical Academy (VMA) and the Interior Ministry, and soldiers helped the injured at the scene.
Radev made the decision after meeting European Commission president Ursula von der Leyen in Varna.
He sent the government plane to Burgas, where it is ready to fly injured people to hospitals in Sofia. Military Spartan transport planes have also been arranged to carry patients to Sofia hospitals.
Updated (10.11, 11:28): More than 10 people have died in two multi-vehicle pile-ups near the Zimnitsa interchange on the Trakia motorway, Yambol regional governor Georgi Chalakov told BTA. One crash was at the 289km mark on the Burgas-bound carriageway. The other was at the 294km mark, before the interchange, on the Sofia-bound carriageway. The interior ministry said fog had cut visibility.