A bus carrying carrying members of Indiana Tech's men's and women's bowling teams crashed on Thursday morning, the school announced on its website.
Passengers injured in the crash received treatment at nearby hospitals, according to the school.
The Courier-Journal in Louisville reported that two victims were in serious condition and that 10 were in fair to good condition.
According to the report, a bus driver is being evaluated by doctors for for "cardiac or possible stroke-like conditions."
Motorist Rick Greed, of Fort Myers, Fla., was driving a budget rental truck just behind the bus Thursday morning. He said the bus appeared to drift into the median, where muddy tracks could seen, before veering back across highway and driving down an embankment and into a ditch.
It wasn't clear what caused the bus to veer, he said.
Greed said police arrived quickly and a handful of medical helicopters landed in succession. Ambulances also came.
"It was a bad wreck," said Kathy Campbell, another motorist who was behind Greed. "I've never seen so many helicopters landing on the interstate in my life."
The bus was traveling from Terre Haute, Ind., to a competition in Smyrna, Tenn.