Salesforce Transit Center is expected to remain closed into November, if not longer, following the discovery of a cracked steel beam Sept. 25. But efforts to shore up the affected area — and elsewhere at the center out of caution — have already begun.

Inspections revealed two cracked beams in the ceiling of the third level bus deck near Fremont Street, which led to the closure of the center and Fremont Street between Mission and Howard streets.

Work on a shoring system beneath the transit center along the affected part of Fremont Street started last week. The street is scheduled to reopen by Oct. 12 in time for the morning commute, the Transbay Joint Powers Authority reports.

The work is being handled by Sheedy Drayage Co., Bigge Crane and Rigging Co. and Herrick Corp.

The cracked beams appear to be a localized issue and no other cracks have been found, according to the Transbay Joint Powers Authority. While a similarly designed area of the transit center at First Street was not found to have any fissures, the TJPA started preparation work Friday night to reinforce the beams in that area as a precaution.

“We have inspected and are continuously monitoring First Street and have found no issues, but because of its similar design to Fremont Street, we think the most prudent course of action is to reinforce First Street as we repair and reinforce Fremont Street," TJPA Executive Director Mark Zabaneh said in a statement. "This will help us reassure the public and make the building as safe, stable and secure as possible.”

The shoring up of that area will take place from 9 p.m. to 5 a.m. to reduce the impact on commuters.

Bus service for the transit center continues to be routed through the Temporary Transbay Terminal at Howard and Main streets.

Once Fremont Street reopens, there will be a two-week testing phase and then plans for permanent repairs — along with a schedule of when to reopen the transit center. It is possible a cause for the cracks may be determined by November, the San Francisco Business Times reports.

One headache the TJPA doesn't expect to deal with is the cost of repairs. The transit center is under warranty for two years and once the cause is determined, the responsible party will be expected to pay, the San Francisco Chronicle reports. That could include general contractor Webcor/Obayashi or its subcontractors.