Officials in San Francisco are looking for answers as to why the city's building inspection department waited years to look into evidence of structural issues involving a luxury high-rise that is sinking more than expected.

The San Francisco Chronicle reports (http://bit.ly/2cqughJ ) the occupied 58-story Millennium Tower has sunk 16 inches since its completion in 2010. Engineers had predicted it would sink just 4 to 6 inches over its lifetime. The newspaper reports the building has also tilted two inches.

Building inspection officials told the San Francisco Board of Supervisors on Thursday that they didn't launch an inquiry into the building until a neighbor called the city last month. That's despite a 2009 letter in which a former official questioned the rate the building was settling in a 2009 letter.

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Information from: San Francisco Chronicle, http://www.sfgate.com