Brown Line trains were on the move again Thursday morning after bitter cold apparently caused a CTA train track to crack on the North Side. Earlier, trains were only operating between the Southport and the Loop stations because a section of the track cracked and a repair crew was sent in to fix it, according to CTA spokesperson Manny Gonzalez.

CTA Brown Line trains are running with residual delays following track conditions that suspended service on Chicago's North Side. Train services were operating only between Southport and the Loop for about an hour.

Riders were also advised to consider other services, including nearby bus routes or buses to other rail lines.

Experts said the extreme cold can make the steel used in railroad tracks brittle, leading to small gaps in the track.