The TTC has resumed streetcar service on Queen Street after a mysterious track issue put two dozen streetcars out of order earlier this week.

A spokesperson for the TTC tweeted Saturday morning that Queen Street was safe, that routine track work likely resolved the cause and that nothing out of the ordinary was found.

On Wednesday, the TTC pulled streetcars from Queen after 25 of the vehicles were found to have damage to their emergency braking systems. The streetcars were temporarily replaced by buses along the 501 route.

While attempting to pinpoint the source of the issue, TTC ran several test streetcars across the length of the entire 501 route with a small camera affixed to the underside to detect any irregularities.

The TTC also reached out to other transit agencies to ask for advice and find out if this was something the other agencies had experienced.

“It is fair to say, it’s a mystery. Our streetcar crews … are all a bit perplexed as to what caused this,” TTC spokesperson Stuart Green previously told the Star.

The TTC typically operates 35 of the new-model Bombardier streetcars on the 501 route. Because buses are smaller, it takes about 90 of the vehicles to provide close to the same capacity as streetcars.

About 55,000 people ride the 501 on an average weekday, making it one of the busiest surface transit routes in the city, according to statistics from the agency.

Initially, the TTC had estimated that the streetcars wouldn’t be functional again until Monday.