This is the terrifying moment truckers try to flee as a fog of deadly ammonia spreads across a motorway bridge in a Serbian city.
Fifty people have been injured and two deaths have been reported, with an autopsy expected to confirm they died as a result of breathing in the toxic gas.
CCTV footage of the toxic fog rolling in across one bridge shows trucks reversing, desperate to escape any contact with the ammonia cloud.
On the central reservation, one pedestrian – apparently already stricken by the chemical – seems to be coughing heavily.
As the fog rolls closer, he manages to stagger away.
Reportedly around 20 tonnes of ammonia was spilled when a tanker on a freight train overturned near the south-eastern Serbian city of Pirot on 25th December.
The accident happened outside a heavily populated area on the section of the railway from Pirot to the village of Stanicenje.
The train was carrying 20 carriages and four of them overturned.
It is unclear how many of the damaged wagons contained ammonia. It is believed that only one of the tanks was leaking.
Nenad Stanisavljevic from the Serbian Railway Infrastructure said that each of the tanks contained about 45 tonnes of ammonia.
With 20 tanks on the train it makes the full deadly payload of about 900 tonnes of ammonia.
He said the special commission had been set up to check that all proper safety standards have been met with regards to the rules governing the transport of dangerous substances.
The extent of the leak was shown in a CCTV video showing the toxic cloud covering the motorway as drivers run for their lives.
The leakage prompted the declaration of a state of emergency after dozens of people were injured after breathing in the gas.
Ammonia is a toxic gas or liquid that is corrosive to animal tissue upon contact and if the exposure is in sufficient quantities, can be fatal.
As the gas dispersed, it was revealed that at least eight people were still hospitalised, although they were reported to be out of danger.
Government officials, a day after the incident, gave the all clear and also said that the water was mostly safe to drink, but people nevertheless for the moment to use bottled water.
As well as those injured from breathing the gas, there are also several people injured as a result of accidents caused because of the thick mist.
