CNN
 — 

Amtrak is restoring service after a slew of train cancellations, primarily in the Midwest due to “a rail-industry control system that continues to experience intermittent communications issues,” according to Amtrak spokesperson W. Kyle Anderson.

The industry control system is used to connect to other railroads, Anderson said. Amtrak trains can operate on freight rail lines, so the trains have to connect to freight railroads to begin their journey – that communication was down.

The system issues began early Friday morning, Amtrak said.

On Friday, Amtrak began tweeting that several trains – many in and out of Chicago – had been canceled. Amtrak’s alert feed on Twitter was still announcing cancellations Sunday morning.

CNN has reached out for comment on how many trains were canceled.