The mayor of the eastern Serbian town of Pirot, Vladan Vasic, declared on Sunday a state of emergency after a freight train carrying ammonia was derailed near the city earlier on Sunday. The dangerous gas leaked into the environment, leading to at least 51 people ending up in hospital for poisoning.

Vasic said in a news conference that 20 train wagons passing through the city were carrying ammonia. Two of these have leaked ammonia into the air and into the nearby river Nisava. As of Monday, a section of the international motorway in this area has been closed, with traffic being redirected towards local roads.

The Serbian Interior Ministry said that 51 people have been hospitalized due to ammonia poisoning. “The main advice we can give is for people to stay at home. Do not turn on air conditioners, to avoid inhaling outside air. We are now all waiting for the cloud of ammonia to pass,“ local website Pirot Plus Online quoted Vasic as saying.

Schools in Pirot also suspended all classes on Monday. Serbia’s Minister for Construction, Transport, and Infrastructure, Goran Vesic, said

“There is no reason to panic because the situation is under control. However, there is reason for caution because the incident is not over yet, and its consequences have not been eliminated,” Serbia’s Minister for Construction, Transport, and Infrastructure, Goran Vesic, told Serbian state television RTS.

Vesic said that two committees have already been formed to determine the circumstances of the incident. adding that the results of will be released to the public at a later date. He said that this was not the first time that a train derailed at the same location, and that the reason was poor infrastructure.