School officials said they were still short 15 drivers by 6 a.m., but they said they should be able to cover those routes with supervisors. Some bus routes were expected to experience delays.
Bus drivers are working without a contract and their union is negotiating with the city's bus contractor, Veolia.
Hundreds of charter school and special education students were left stranded Monday because there were not enough drivers. Supervisors and managers jumped in Tuesday to fill some routes.
Mayor Marty Walsh says drivers not showing up to work is "unacceptable." The mayor vowed to get to the bottom of the problem.
City officials say they hope the issue will be fully resolved by next week.
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