Commuters contended with delays along several subway lines early Wednesday morning after a power outage impacted train signals, the MTA said.

A, E, F and J trains all saw significant delays due to the loss of power, according to the MTA.

As of 10 a.m., trains along those lines were running back on schedule, per the MTA’s website. 

The MTA said the cause of the loss of power is still unknown, though they have ruled out excessive heat as a possibility.