KIEV, July 19 - At least 143 people have been hospitalized in Ukraine for symptoms blamed on a toxic cloud formed by chemicals leaking from a crashed train near Lviv, the Healthcare Ministry reported Thursday.

The number has doubled over the past 24 hours, two days after the train crash, suggesting the toxic cloud may have spread to affect more people. Forty-three of those treated so far are children, the ministry said.

Prime Minister Viktor Yanukovych visited the residence of President Viktor Yushchenko in Crimea on Thursday to brief him on the progress of the clean-up operation, Yushchenko's press service reported.

Yanukovych also joined a meeting of the National Security and Defense Council, Ukraine's top security body, which had apparently been called to discuss this and other matters.

Meanwhile, government officials insisted Thursday the worst was over in containing the spread of the toxic cloud, while progress has also been made to remove the overturned rail tanks and cars after the Monday crash.

"The situation is stable and under control," a spokesman at the Emergency Situations Ministry said.

However, independent toxicology experts were cautious on the accident.

"This accident is very dangerous, and its consequence can be unpredictable," Zofia Kubrak, a toxicology expert at Lviv Medical University, told The Associated Press on Thursday. "I doubt that there is no threat for people now."

The train, traveling from Kazakhstan to Poland, was derailed at about 4:55 p.m. local time on Monday in the Lviv region, overturning 15 rail tanks of phosphorus. Six rail tanks caught fire, spewing toxic smoke over an area of about 90 square km, where about 11,000 people live, according to the emergency ministry.

The firefighters managed to extinguish the fire within hours after the crash, but the toxic cloud continued had continued to pose threat to the people.

Yellow phosphorus is a waxy solid which is stored under liquid because it ignites on contact with oxygen. Phosphorus compounds can be extremely toxic. (jp/ez)