The North Carolina Department of Public Inspection sent a statewide memo to school districts Friday morning demanding that certain bus types must be reinspected. The new requirement comes after two Charlotte-Mecklenburg School buses caught fire within the first few months of the 2017-18 school year.

"This message shall serve as a notice that every model year 1998-2003 bus with a Caterpillar engine must be inspected again, and if needed, repaired," the NCDOP said in their memo.

The NCDOP also said the two bus fires appeared to have started in the engine compartment.

RELATED: Parents demand answers after CMS school bus fire

RELATED: CMS bus catches fire in southwest Charlotte

On Tuesday, a CMS bus caught fire in southwest Charlotte. The bus was not carrying children at the time of the fire. But the fire caused concern for parents as it was the second bus that caught fire within the start of the school year.

On October 19, 16 students were evacuated after a different bus caught fire in east Charlotte.

CMS announced Thursday that the investigation into the fires still remains active and that the manufacturer of Bus No. 188, Thomas Built, has provided a third-party investigator to join the investigation. An investigation into the cause of a fire on Bus No. 164 on October 19 was inconclusive. CMS Transportation Services provided an update on October 23 to all technicians to ensure a thorough mechanical inspection of all buses that utilize the Freightliner 3126 engine.