A fire aboard a Charlotte-Mecklenburg Schools bus that sent six students and their driver scurrying to safety has prompted N.C. officials to instruct all school districts across the state to inspect their buses.

The N.C. Department of Public Instruction said officials believe the school bus blaze was caused by worn wire coverings – an issue that might be found on Thomas Built Buses received by schools about 13 years ago.

On Feb. 8, bus driver Lindora Richardson was driving students home from Chantilly Montessori School when she noticed a burning smell and stopped the bus. Smoke soon began pouring from the front of bus No. 295 as Richardson moved the students off the bus, lowering some out the emergency back door.

The fire spread quickly, sending flames and thick, black smoke into the air. No one was injured, and Richardson was hailed as a hero.

Last week, an inspector from Thomas Built and an independent fire inspector examined the charred bus – a Freightliner FS-65 with a Thomas Built Buses body built in 1999. State officials also arrived in Charlotte to determine whether any warning or advice needed to be sent to other districts.

State officials said initial reports indicated that the fire began in the switch panel. But further inspection revealed that an intake heater wire likely rubbed against the metal heater shutoff valve, causing the wire’s covering to wear through and possibly causing a short that led to the blaze.

On Wednesday, state school officials announced the department had directed all local school system transportation departments to examine a number of Thomas Built Buses in their fleets.

State school transportation chief Derek Graham said officials are seeking clarification from Thomas Built Buses. He said it appears that buses with the possible problems are ones received in shipments between summer 1998 and 1999.

A memo was sent Tuesday to school districts across the state, instructing transportation departments to inspect “all of the school buses and activity buses in this date range for similar wiring issues," officials said. It wasn’t immediately clear how many hundreds of buses statewide could be affected.

Guy Chamberlain, associate superintendent for Charlotte-Mecklenburg Schools, said the school district has about 100 buses that could be affected by the problem. He said CMS began examining the buses for the wire covering issue last week.

“As soon as the first inspector noted it a week ago, we started at looking at that,” Chamberlain.

So far the inspections, which are expected to be completed within the next few days, have not discovered any other worn-through wires, he said.

Thomas Built Buses is completing a more detailed report on the incident, state officials said.

“Now that we have more information about the likely cause of this fire, we want to use this information to be more diligent in preventing any other incidents,” Graham said.

A spokeswoman for Thomas Built, a subsidiary of Freightliner, could not be reached for comment Wednesday afternoon.

Officials said it appears the cause of the Feb. 8 fire is not the same problem that has caused flames to erupt on buses of the same make and model in North Carolina and elsewhere in recent years.

A similar bus in York, S.C., was engulfed in flames in a parking lot last year after the driver noticed a leak.

A Thomas Built bus fire prompted Greenville, N.C., television station WNCT to investigate other fires around the state. The station found that at least four of five buses that caught fire between 2010 and 2011 were FS-65 buses. Four of those fires were caused when wires in the engine compartment dropped onto the turbo manifold, an engine part that gets hot, officials told WNCT.

Chamberlain, who called the Charlotte fire a “unique event,” said he wasn’t aware of a similarly-caused fire in North Carolina or elsewhere.