NORTH CONCORD (CBS SF) — Buses that have taken BART riders between East Bay stations where a still-mysterious glitch knocked train cars out of commission last week are being replaced by another temporary solution, the agency’s officials said Friday.

A pair of train shuttles, which were introduced within only certain hours on Monday, will instead take riders between the Pittsburg/Bay Point and North Concord/Martinez station throughout all of BART’s service hours.

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More than a week after electrical issues first afflicted part of the BART line between the two stations, the agency’s officials still don’t have a timeline for when normal service will be restarted there.

First reported the morning of March 16, a problem determined to be a voltage spike damaged around 50 train cars between the stations. The source of this voltage spike has eluded BART crews even after an exhaustive investigation.

“We’re a little perplexed right now,” BART assistant general manager Paul Oversier told the BART board of directors at their meeting Thursday morning.

At that meeting, BART officials expressed dissatisfaction with the interim measures that have been necessary to keep regular riders moving on the affected line.

When people use the train shuttles to get between the stations, they have to off-board and get on a different train to get to other destinations on BART.

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“We need to understand how significant this is to people,” BART director Joel Keller, who represents the affected stations, said.

Keller said he took the shuttle to Thursday’s meeting, and while it works, “it’s not what people are accustomed to, it’s not what they expect, it’s not the level of service that we have provided people for 20 years. It’s a step down in service.”

BART officials said Friday that riders who have to travel between the two stations will have to rely on these train shuttles until further notice.

Meanwhile, BART crews continue working around the clock to identify and correct the problem, the agency’s officials said.

Three outside consultants and new diagnostic equipment are being utilized to help in that.

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Other plans to restore normal service, such as using a model of train cars on the line that has not been affected by the glitch, are also being explored.