Tests revealed no significant air, soil or water pollution in the area, where a train carrying yellow phosphorus, a poisonous substance, 0.05 to 0.15 grams of which is enough to kill a human being, derailed and caught fire Monday.
Official reports said 20 people were hospitalized and 14 settlements with a total of 11,000 residents were affected.
The cloud of poisonous smoke subsided near the site of the accident and no neighboring countries, including Belarus, are in danger.
The Ukrainian government said the accident was the country's largest man-made disaster after the 1986 Chernobyl tragedy.
Ukrainian rescuers continued clean-up efforts Tuesday evening as several spot fires were reported at the site. Emergency workers continued to cover phosphorus concentrations with a mixture of sand and sodium carbonate, as the substance is highly inflammable and the hot weather in Ukraine could cause more fires.
Kazakhstan's emergencies ministry have sent a disaster recovery team, as Ukraine has no experts trained to handle phosphorus.
A special commission has been set to investigate the accident and criminal proceedings have been launched. The traffic is expected to be resumed within 24 hours.
The poor condition of cars, as well as damaged rail tracks and the failure to comply with rules for transporting dangerous cargo, have been cited as the main reasons for the accident.