Emergency crews are battling a fire outside the Ukrainian capital, Kiev, following a huge blast at a fuel depot.
The blaze broke out on Monday evening, and one worker at the plant died.
The explosion on Tuesday morning left several firefighters reportedly injured or missing.
Three firefighters were unaccounted for and another six were taken to hospital, officials said, as the fire spread to at least 16 tanks, most of them storing petrol.
The fire at the depot, next to Hlevakha airbase and near the village of Vasylkiv, sent a huge pall of smoke over the surrounding area.
The army has been clearing a munitions storage facility, located about 50m (164ft) away, according to Oleksandr Turchynov, secretary of Ukraine's national security and defence council.
Fears it could spread
The blaze broke out on Monday evening in one tank and spread to neighbouring containers, Ukraine's emergencies ministry said (in Ukrainian).
An official from Ukraine's petrol industry told the BBC that the explosion had occurred at 08:30 local time (06:30 BST) on Tuesday.
Interior Minister Arsen Avakov tweeted: "There has been an explosion at the oil depot near Vasylkiv. A huge one."
The casualties were being treated in hospital for burns and poisoning.
Of the 16 tanks on fire, eight were said to have a capacity of 900 cubic metres (32,000 cu ft) each.
Two hundred firefighters were trying to bring the fire under control amid fears it could spread to an adjacent depot.
People in a 2km (1.24 miles) zone around the petrol containers currently on fire have been evacuated, Mr Turchynov said.
It was not immediately clear what might have caused the blast.