An obstruction on the BART track in the Transbay Tube caused major delays Thursday afternoon.

The issue, described by transit officials as “an obstruction on the track,” caused major delays in the Antioch, Dublin/Pleasanton, Warm Springs, Richmond, SFO, Millbrae and Daly City directions, BART officials said.

Trains were single-tracking through the Transbay Tube at a reduced speed while crews were en route to clear the track, BART officials said. Both tracks reopened shortly afterward.

We are currently single tracking through the Transbay Tube at reduced speed due to an obstruction on the trackway. Crews are on their way to clear it. https://t.co/1VcRAblop3 — SFBART (@SFBART) November 21, 2019

Lauren Hernández is a San Francisco Chronicle staff writer. Email: lauren.hernandez@sfchronicle.com Twitter: @LaurenPorFavor