Seven workers were injured on Tuesday in a series of explosions at a munitions depot near the village of Lozenets in southeastern Bulgaria, close to the Petoluchkata road junction on the Sofia - Bourgas highway.
It is still not clear what triggered the blasts.
The air pollution indicators in the area of the accident are within the permissible levels, the state-run Bulgarian National Television (BNT) reported on Wednesday morning quoting the Civil Defence head.
Three workers are still missing, BNT added.
The explosions began at 2:40 p.m. (1240 GMT) at the depot owned by local private company Bereta Trading. At that time 13 workers were in the facility and they were evacuated.
Two after-blasts took place during the night, BNT added.