(CNN) -- One freight train rear-ended another Friday afternoon, sending debris into a passing third train, authorities in Porter County, Indiana, said. Firefighters put out flames among the jumble of derailed cars.
Two crew members on the train that struck the back of the other suffered non-life threatening injuries, officials told CNN.
CSX said it appeared there were no significant leaks or spills of hazardous materials, "but inspections of all loaded and empty hazardous materials cars are under way," it said in a statement.
The three-train accident occurred about 1:15 p.m. Friday about 11 miles northeast of Valparaiso, said David James of the county's highway department.
The first train, with two engines and 77 cars, was stopped on the westbound tracks, said Sgt. Larry LaFlower of the Porter County Sheriff's Department. CSX said it was investigating why the first train was stopped.
A second train, with two engines and 60 cars, hit it from behind, LaFlower told CNN.
The third train, with 48 cars, was moving on a parallel track. "It struck the wreckage and derailed itself," the sheriff's spokesman said. He did know which direction that train was moving in.
James said he did not know what speeds the trains may have been traveling.
"The trains carried a wide variety of freight, including three rail cars of flammable products," CSX said in a statement. "Also in the incident are a number of empty hazardous materials cars."
The train struck from behind was carrying empty ethanol tankers, according to LaFlower.
The county's hazardous materials team was on the scene, and residents of about 50 homes were evacuated, authorities said. CSX said it was assisting officials with the evacuation.
James said the stretch of railroad was in an agricultural section of the county. "It's been like a spring day here," he said of weather conditions.
CSX said it was still determining the total number of derailed cars.
The accident occurred near county roads 550 East and 600 North.
The National Transportation Safety Board arrived later Friday and was leading the investigation.
CNN's Phil Cantor contributed to this report.