The Latest: Temporarily shoring up 2 beams is a priority

The Latest on the closure of San Francisco's new transit center (all times local):

2:55 p.m.

A San Francisco official says his first priority is to shore up two cracking beams so a $2.2 billion transit center can re-open while engineers search for a permanent fix.

Transbay Joint Powers Authority executive director Mark Zabaneh said Wednesday he expects the Salesforce Transit Center to be closed through next week.

Workers discovered the first crack early Tuesday while installing roofing tiles. The second crack was discovered Tuesday night.

The center was shut down during Tuesday's evening commute.

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2:15 p.m.

Construction experts say it's exceedingly rare for steel girders that support buildings to crack like those in San Francisco's new $2.2 billion transit center.

The experts said Wednesday that cracks can appear in bridge girders because of the fluctuating vehicle weight crossing the structure. But cracked steel in the transit terminal support the same weight all the time.

Two San Francisco engineers say it's too early to point to a likely cause, but they say investigators will look at the beam's U.S. manufacturers, building's design and installation process.

Engineer David Friedman says the beams were likely delivered and installed without the crack two years ago, but the flaws appeared once they started supporting a rooftop garden and other loads.

Engineer Joe Maffei says the cracks could have been caused during installation, perhaps by quickly rising and falling temperatures caused by a welding torch.

Workers discovered the first crack early Tuesday while installing roofing tiles.

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1:25 p.m.

A San Francisco official says a new $2 billion transit terminal that shut down over a cracked support beam has a second adjacent beam that also shows signs of cracking.

Salesforce Transit Center executive director Mark Zabaneh said Wednesday that the facility would remain closed "at least through the end of next week" as inspections continue.

He says the problems are localized to that area of the transit hub but that officials don't yet know what's caused the cracking.

Workers discovered the first crack early Tuesday while installing roofing tiles.

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12:55 p.m.

A resident of the San Francisco neighborhood where a transit terminal is closed out of safety concerns says the $2.2 billion used to build it could have gone to other priorities.

Julianna Cheng lives in the South of Market neighborhood where warehouses have been replaced by luxury high-rise condos and gleaming office towers amid a construction boom in the last few years.

The 32-year-old says it's disappointing but kind of amusing that Salesforce Transit Center was shut down only weeks after it opened.

City officials in 2012 approved legislation to boost height limits on new buildings in anticipation of the transportation hub opening and as part of an effort to lure technology companies from Silicon Valley.

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12:20 p.m.

The mayor of San Francisco says the city's new $2 billion transit terminal where a crack was found in a support beam will stay closed until officials determine it's safe to reopen it.

Mayor London Breed said she visited the Salesforce Transit Center on Wednesday to meet with officials assessing the crack found Tuesday by workers installing roofing tiles.

Breed says a thorough investigation will be conducted to determine what caused the crack, who is responsible and when the transportation hub can safely reopen. She didn't say when that would be.

Officials closed the center during Tuesday afternoon rush hour. Buses are being rerouted to a temporary transit center about two blocks away.

The five-level center that opened last month includes a bus deck, a central entrance hall and a rooftop park with an outdoor amphitheater.

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12 a.m.

The so-called "Grand Central of the West" is closed out of safety concerns after workers discovered a crack in a support beam of the $2 billion transit terminal that opened just last month.

Executive director Mark Zabaneh says workers discovered the crack early Tuesday while installing roofing tiles at the Salesforce Transit Center. He said structural engineers would be working at the building Tuesday night to assess whether it is safe for people to return.

Enveloped in wavy white sheets of metal veil, the five-level center includes a bus deck, a towering sky-lit central entrance hall and a rooftop park with an outdoor amphitheater. Zabaneh said American steel was used in the center's construction.

Buses were rerouted to a temporary transit center about two blocks away.