The Environmental Protection Ministry said levels of phosphorus compounds in the air were up to 23 times higher than normal where a freight train carrying yellow phosphorus derailed and caught fire in western Ukraine on July 16.
A toxic cloud released by the fire contaminated an area of 90 square kilometers, and some 70 people were hospitalized, 19 of them children.
Deputy Prime Minister Oleksandr Kuzmuk, who a day earlier compared the contamination to the Chornobyl nuclear disaster of 1986, said on July 18 that people in the area had no reason to worry.
Kuzmuk said it was safe to breathe the air, drink water from the wells, harvest crops, and swim in the rivers.
"All the data that was gathered yesterday and analyzed today gives me every right to affirm that, from the ecological point of view, this area is no longer contaminated," he told journalists after a meeting of disaster-relief headquarters.
However, RFE/RL's Ukrainian Service correspondent Viktoria Papadyuk says people in the contaminated area do not feel that way.
She says more than 1,000 people are reported to have left the affected area, and that officials from Ukraine's Emergency Situations Ministry told her some 700 people had asked for medical help.
Transport Minister Mykola Rudokovsky said failure of the liquid-phosphorus containers was a possible cause of the spill, but Kazphosphate, the Kazakh company that owns the shipment, denied this.
The train was traveling from Kazakhstan to Poland when it derailed near the Polish border.
(with Interfax-Ukraine, UNIAN)