6.0-magnitude earthquake rocked Northern California early Sunday morning, damaging buildings and injuring more than 80 people -- and led Napa officials to realize that some property owners in the city's historic downtown had missed a 5-year-old city deadline to retrofit their buildings.

Napa passed an ordinance in 2006 that required property owners to update any unreinforced brick buildings by the summer of 2009.

Five years later, a "small handful" of buildings still did not meet seismic codes, said Rick Tooker, the city's community development director, during a televised news conference.

"That deadline has come and gone," Tooker said. He said the city was "actively pursuing" the property owners that have not performed the work.

It isn't clear whether the unreinforced buildings were among those that sustained damage during the early-morning earthquake, Tooker said.

The 2006 ordinance required inspections of all unreinforced masonry buildings. The law does not apply to public schools, hospitals, state-owned buildings and family dwellings. The city offers some financial aid to property owners for planning and construction work, according to the ordinance.

Napa first developed a list of unreinforced commercial buildings after the Loma Prieta earthquake in 1989, which killed more than 60 people in the Bay Area, local news outlets have reported.

Los Angeles and other cities also have retrofitting ordinances.

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