A labor move by Muni workers calling in sick is expected to cause major delays in the morning commute Monday.

Officials from the San Francisco Municipal Transportation Agency are warning riders to expect delays, as bus and light-rail operators failed to come into work as part of a labor dispute.

Reports say 400 of 600 buses were not operating as of 6:30 a.m., and all lines were seeing up to 30-minute delays.

BART will honor Muni fare in San Francisco and Daly City. All express and limited buses will stop at every stop. There is no cable car service.

In a post on Twitter, Muni officials warned riders to "expect major delays on Muni today. Working to balance service the best we can across the city. Apologies for this inconvenience."

Muni operators on Friday voted on a new labor agreement, but that has not yet been ratified.

The proposal would raise operators' pay to $32 per hour, making them the second-highest-paid transit workers in the U.S.

• BART Union Worker Pay Compared to Other Transportation Agencies