The Mayor of the city of Pirot declared Sunday a state of emergency in this eastern Serbian city after a freight train derailed near the city, releasing ammonia into the air.

The train derailed on Sunday, causing the leakage of ammonia and the dispersion of a large amount of gas into the atmosphere.

Pirot Mayor Vladan Vasic told a media conference that 20 wagons were carrying ammonia, of which two leaked ammonia into the air and the Nisava River.

A section of the international motorway in this area has been closed due to the incident and traffic is redirected to local roads.

The Emergency Management Sector of the Serbian Interior Ministry said that 51 people have been hospitalized due to ammonia poisoning.

„The main recommendation is that people do not leave their homes, do not turn on air conditioners so that outside air does not enter and we all wait for that cloud of smoke to pass,“ Pirot Plus Online quoted Vasic as saying.

Vasic also said classes would be suspended Monday in all Pirot schools.

Serbian Minister of Construction, Transport and Infrastructure Goran Vesic said there was no reason to panic because the situation is under control, but there is reason to be cautious because the incident is not over and its consequences have not been eliminated.

He told the Serbian state TV (RTS) that the people should adhere to the instructions issued by the state bodies so as to overcome the crisis with as little damage as possible and protect the people’s lives, which, he said, was the most important thing at this point.

Minister Vesic said two committees have been formed to determine the conditions under which the incident took place, adding that the results of will be released.

He said this was not the first time that a train derailed at the same location, and that the reason was poor infrastructure.

The Ministry of Environmental Protection said it was monitoring the situation.