San Francisco, California (CNN) -- The San Francisco-Oakland Bay Bridge will remain closed Monday morning, and officials said Sunday that they can't predict exactly when it will open for business again.
Engineers headed into their sixth night of repair work Sunday with plans to stress-test work done thus far, said Bart Ney, a spokesman for the California Department of Transportation.
Crews performed stress tests Saturday night, Ney said at a news conference, but the results showed the potential for metal grinding, which could cause another break.
Two steel rods and a steel crossbeam plummeted from the bridge Tuesday night. Vibrations in the rods, affected by strong winds, caused the break, officials said.
After stress tests prove successful, engineers will do a vibration test, Ney said. They might have trucks driven on the lower deck of the bridge to simulate the effect of vibration, he explained.
With the ongoing repairs, commuters must make alternate plans for their morning travel.
"We're not making a prediction on when the bridge will reopen," Ney said. "I know that is frustrating to motorists, and we apologize, but we don't want to make a false prediction. We want to put safety first, and we want to basically make sure everyone feels comfortable with the repairs that we have done."