"An ARB investigation showed that MTS failed to meet transit fleet vehicle requirements, and did not inspect their heavy-duty diesel vehicle fleet," according to a statement issued by the state regulatory agency.
Rob Schupp, an MTS spokesman, said the majority of the fines are due to late testing on diesel buses and other vehicles.
"They passed the test, we just missed our deadline," Schupp said.
According to Schupp, only 97 of MTS' 551 vehicles are diesel, and most if not all, will be replaced in the next two years.
"We've got one of the cleanest fleets in the nation," he said.
Temperatures will continue to warm through the week, with slightly cooler temperatures for the weekend.
Five people were injured in a three-car crash in the Rolando area on Sunday after an apparent road-rage incident. It happened about 1:30 p.m. on University Avenue at College Avenue, according to the San Diego Fire-Rescue Department.
Another successful Comic-Con is in the books. The four-day pop culture convention came to an end Sunday, but even in its final hours was packed with things to see and do.
Vince Velasquez allowed two hits over seven innings and the Philadelphia Phillies beat the San Diego Padres 5-0 Sunday for a doubleheader split.
A man stole a brand-new luxury car out of a Kearny Mesa dealership's lot and led police on a lengthy chase down San Diego freeways on Sunday.
San Diego Comic-Con is in full swing and so is the superhero-themed fashion! Celebrities like Sarah Paulson, Sonequa Martin-Green and Camila Mendes, among many other stylish ladies, rocked a bevy of leather, nylon and pleather to attend the annual comic book convention.
Detectives are investigating the circumstances surrounding a man who died Saturday morning on a sidewalk in Old Town.
A suspected drunk driver was shot by sheriff's deputies after leading them on a pursuit across North County freeways Friday night, the San Diego County Sheriff's Department said.