4:15 p.m. update: The train is gone.

It was a break in a "knuckle" – train speak for the joint that connects cars – that triggered the Union Pacific train to automatically make an emergency stop, a Union Pacific spokesman said. It blocked Oltorf Street near Lamar Boulevard for hours.

The knuckle was fixed, but then the train's air brakes had to be repressurized. Once that was done, another locomotive came to its aid to help push the train up a slight incline and on down to its destination in San Antonio, the spokesman said.

Earlier: A Union Pacific train experiencing mechanical issues is stuck in South Austin and is blocking Oltorf Street just east of Lamar Boulevard.

The train could have the street blocked for up to three hours, Austin police said. A technician is headed to the scene, but it might require another train engine to get the stuck train moving.

The train went into "emergency mode," according to Austin police and shut down. Because it is slightly uphill where it stopped, the other engine might be necessary to move the train.

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