SAN FRANCISCO, California (CNN) -- Crews are scrambling to repair a crack found on the San Francisco-Oakland Bay Bridge during a planned closure, but officials said Sunday they don't know if the bridge will reopen Tuesday as scheduled.
The bridge was closed Thursday as part of a planned seismic retrofitting project.
"Right now, we don't have an estimate on how long it's going to take," Bart Ney, spokesman for the California Department of Transportation, or Caltrans, told reporters. "And we can't say for sure the Bay Bridge will be able to open on Tuesday morning."
The bridge was closed Thursday as part of a seismic retrofitting project that requires cutting out and replacing a double-deck portion of the east span. During an inspection of the east span of the bridge, workers found a crack in one of the eyebars on the side of the structure, Ney said Saturday.
"It's a significant crack," he said, "significant enough to have closed the bridge on its own."
Officials said Sunday the crack was not detected during the last inspection of the bridge two years ago. However, the crack had rust in it, so apparently it has been there a while.
"A lot of good work got done last night towards making this repair," Ney said Sunday. Materials have already arrived on site, with others en route, he said.
The crack is "far away" from the planned work taking place and unrelated to it, he said.
About 280,000 vehicles cross the landmark bridge every day, according to Caltrans.
A 50-foot section of the bridge collapsed in 1989 during the Loma Prieta earthquake, prompting efforts to make it quake-tolerant.
CNN's Janet DiGiacomo contributed to this report.