NEW ORLEANS – The absence of a $3 part may have let tires roll off of a semitrailer truck, killing a Tulane University student from Minnesota, a Mississippi transportation official said.

One of two 3-inch locking washers designed to keep truck wheels tightly secured was missing from the trailer, according to Willie Huff, director of the department’s Office of Enforcement.

Two wheels joined together rolled into a rest stop on Interstate 10 in Mississippi, killing Margaret (Meg) Maurer of Forest Lake on March 5. Maurer, 21, who was studying ecology and evolutionary biology, and her classmates were heading from the Mardi Gras celebration in New Orleans to a cabin in the Blue Ridge Mountains in North Carolina.

The conclusion blaming the missing metal ring is preliminary, Huff said.

Gene Patten, vice president of safety and compliance for the truck’s owner, Dana Transport Inc. of Avenel, N.J., said he couldn’t comment.

Patten referred the Associated Press to an attorney who didn’t immediately return a call for comment.

Huff said that when inspectors unpacked the outer hub of the wheel assembly after Maurer’s death, they found only one of the two washers that are used to lock the large nuts holding the wheels in place. The missing ring wouldn’t have broken off, he said.

In addition to Dana Transport, the truck is listed under a related company, Suttles Truck Leasing of Demopolis, Alabama.

Both companies are in good standing with the Federal Motor Carrier Safety Administration, with “satisfactory” ratings and a better-than-average record on crashes and vehicle safety.

Huff said the missing ring would not have been detected in the kind of unannounced roadside inspections that are logged into the federal database.

“To inspect that truck for that deficiency, you’d have to take all the wheels off the truck,” he said.

“It’s also something that probably would not be noticed with a pre-trip inspection or roadside inspection unless the wheel is wobbling,” he said. “More than likely, this wheel wasn’t wobbling. It just slipped off.”