SAN FRANCISCO (KCBS) — The Millennium Tower, one of the city’s most prestigious addresses, is sinking fast.

The luxury high-rise is home to celebrities like Joe Montana and Hunter Pence. Condominiums in the 58-story building have price tags as high as $10 million.

According to KCBS and Chronicle Insider Phil Matier, an engineering report says that the 58-story, $350 million luxury high rise has sunk by 16 inches since its completion in 2009. It’s also tilted by two inches to the northwest.

The news did not inspire confidence among building residents.

“It’s scary,” said resident Mark Weir. “I’ve seen a lot of surveyors, so I kind of thought something was up like that and I’m pretty shocked. ”

“The leaning tower of San Francisco,” said another Millennium resident, Joe Keegan.

Who is to blame for the problem depends on who you ask.

Millennium Tower officials say the sinking was triggered by excavation work for the nearby Transbay Terminal. But Transbay officials point out that the tower had already sunk by ten inches before the Transbay dig began. They blame the problems on the way the high-rise was built.

“To cut costs, Millennium did not drill piles to bedrock,” said the transit authority in a statement. Had it done so, “the tower would not be tilting today.”

In fact, the Millennium Tower sits on an area of mud-fill. It is not steel-framed, and instead relies on shear walls, columns and beams. The building is anchored over a thick concrete slab and its pilings extend about 80 feet into dense sand, not into the bedrock which lies about 200 feet below street level.

For that reason, the transit authority says it went to considerable expense to protect its high-rise neighbor, before it even broke ground on the Transbay Terminal.

“Aware that the Millennium Tower foundation failed to reach bedrock and was therefore inadequate to support the Tower, the TJPA took the extraordinary step of spending more than $58 million to install an underground buttress between the Millennium Tower and the Transit Center site before the TJPA began its excavation for the new Transit Center,” the statement said, denying any responsibility for the settlement of the Millenneum Tower.

In earthquake-prone Northern California, the sinking is raising major concerns.

Still, P.J. Johnston, spokesman for Millennium Partners and principal owner Sean Jeffries, said a 2014 independent safety review “determined the settlement has not significantly affected the seismic performance of the building, and does not represent a safety risk.”

Johnston says several other downtown buildings have similar foundations, including the Intercontinental and St. Regis hotels.

Some shifting was expected. The builder predicted 6 inches of sinking over the lifetime of the high-rise.

Greg Deirlein, director of Stanford’s Earthquake Engineering Department says the sinking problem is “significant… and of concern.”

He said if he was one of the people living there, “I would be concerned for my investment.” When buildings settle, it can cause cracks in the walls and other problems.

Except for “minor repairs to sidewalks and connections at the ground level” Johnston says there have been no complaints about damage to residents’ condos.

Despite assurances, the Millennium Tower’s homeowners association has hired independent engineering consultants and says they are looking at their “legal options.”

The city’s Department of Building Inspection also said there were unaware of any safety problems.

So far the only signs have been cracks in the garage and an ongoing problem with the sidewalk.

“There has always been the great speculation that the building was sinking,” said former San Francisco Mayor Willie Brown. “And – obviously, based on the numbers – it is.”

Three years ago, Ashok Vaish paid just under $2 million for his tower digs.

“Mine is one of the cheaper apartments,” said Vaish.

When asked if he was worried about it sinking even more, Vaish replied, “It will sink for sure. It’s the tilting that you worry about more.”

Vaish said there were also concerns about property values going down.

“There will be a temporary shock to everybody who lives here,” explained Vaish.