First CMS school bus fire was a puzzle. Second raises alarms across North Carolina.

State, local and industry experts scoured the remains of Bus 188 Wednesday after it caught fire Tuesday, while police reviewed video of the bus lot for any sign of tampering.

Charlotte-Mecklenburg Schools officials say it’s vital to figure out why two similar buses caught fire on the road within the past month, even though no one was seriously injured.

“We have now had two fires. That’s a very unusual situation in our district. That’s unusual across the nation,” CMS Chief Operating Officer Carol Stamper said at a Wednesday news conference. “As soon as we have something to act on, we will act.”

CMS continues to struggle to find mechanics to service its large and growing fleet, with eight of 42 mechanic positions vacant Wednesday. But she said buses are getting all the regular inspections required, as well as daily checks by drivers before and after each run.

“There is a lot of overtime,” she said. “We are not short-cutting anything.”

The two buses that caught fire were both the same make and model, known as a Cat 3126 Freightliner Thomas Built bus, and were both spares that had been pulled into service. They’re among 259 in the CMS fleet of more than 1,400 buses, which includes regular, spare and activity buses, and about 3,000 taking North Carolina children to and from school.

That makes diagnosing and fixing the problem essential for students and drivers across the state. Stamper said she was fielding calls from nearby districts Wednesday.

After the first bus caught fire on Oct. 19 while taking 16 students home from South Mecklenburg High, CMS called in state and fire officials to figure out what went wrong. Their findings were inconclusive, and CMS inspected all 259 of the similar buses, including Bus 188.

There were no trends or patterns of problems that might create a fire risk, she said Wednesday.

On Tuesday, Bus 188 made its morning runs safely but caught fire about 1:45 p.m., as it was leaving the lot to make its first afternoon run to Olympic High. No students were on board, and the driver pulled over and got off after smelling smoke.

Stamper said the fire is being investigated by experts from CMS, the North Carolina Department of Public Instruction, Thomas Built and Carolina Thomas, the Greensboro dealership that sold the buses to CMS.

She said it’s premature to pull the buses off the road or take any other action until there’s a clearer insight into possible causes. CMS has 1,078 buses carrying more than 90,000 students to and from school, and pulling out more than 200 of them would disrupt schedules, Stamper said.

“We are all thinking in the back of our minds what Plan B might be,” she added.

Stamper said CMS will notify families and the news media when there are findings to report.

She added that the district has taken action to avert another hazardous bus situation that kicked off this school year, when the rear wheels of a school bus fell off in morning traffic, wrecking a car. That was blamed on a mechanic’s failure to tighten lug nuts with a torque wrench after servicing the brakes.

After that CMS bought Wheel-Check indicators that make it easier for drivers to spot a loose nut. They are being installed on all buses, Stamper said.

This story was originally published November 15, 2017 at 2:38 PM with the headline "First CMS school bus fire was a puzzle. Second raises alarms across North Carolina.."