(Reuters) - Indiana environmental officials are monitoring the aftermath of a freight train derailment and fire in northern Indiana Tuesday morning that may have caused hazardous substances to enter the Elkhart River. Amy Hartsock of the Indiana Department of Environmental Management said it is too soon to know if any of the molten sulfur or toluene carried by some train cars entered the river, which is fed by a nearby wetland. Environmental officials do not know if foam seen on the river is a result of the derailment. "We are watching it very closely," Hartsock said. ...