County units made their way to Thompson Road Tuesday, after receiving reports of a possible chlorine leak. Deputies made contact with Eagle Pass Fire Marshal Cardona upon arrival and were told that the information given to them by Union Pacific officials was that subjects advised the conductor of the train of a dark cloud around a specific tank carrying chlorine. The conductor stopped the train and evacuated the area and a Union Pacific HAZMAT team was activated. No citizen evacuation was required at the time of the incident. Union Pacific police took over investigations.