San Francisco city building inspectors have issued a violation notice against the Millennium Tower after NBC Bay Area’s Investigative Unit exposed an apparent fire safety risk to the tilting structure.

“It’s a step in the right direction, the entire thing is unsettling,” said city Supervisor Aaron Peskin about the notice of violation, which the city issued a week after NBC Bay Area’s report about the fire safety concern.

A consultant issued a warning in a December 2016 report commissioned by the Millennium Homeowners Association, following odor complaints by condo owner Paula Pretlow.

The consultants, Allana, Buick and Bers, traced the mystery odors to gaps between the façade – or curtain wall – and the core of the concrete and steel tower.

Those curtain wall gaps, the report found, were likely getting worse because of the tilting 58-story structure, creating gaps that posed “a life and fire safety hazard to the occupants.”

That’s because experts say smoke and flames can shoot through such gaps, making it easier for a fire to jump to a higher floor.

But for more than a year, the fire safety warning was kept secret. A week after NBC Bay Area’s report on the warning, the city Department of Building Inspection quietly issued the violation notice based on the 2016 findings.

The Dec. 20 notice cites “a breach in the fire and smoke barrier has been represented” in the consultants’ report. “Additionally, the expert cites shifting of the curtain wall panels… and suggests the issue may be more widespread.”

Millennium officials now must either find a different expert who will vouch for the building’s fire safety, gaps and all, or come up with a fix.

Neither the tower’s developer, Millennium Partners, nor the tower Homeowners Association lawyer would comment about the violation notice.

Supervisor Peskin – a frequent critic of the city’s handling of the Millennium case – says the city is still not doing enough.

“I wish the city would take it a little more seriously, and be more aggressive about it,’’ he said, “but all and all, they are finally – only because of media attention – paying attention to the issue and they finally issued a notice of violation.”

The city has given Millennium officials until Jan. 19 to respond.