A water main break causing a leak in the South Concourse at Union Station affected some Metra commuters Friday afternoon.

A sprinker pipe burst about 4 p.m. and sent water onto part of the South Concourse, Amtrak spokesman Marc Magliari said. It took crews about 30 minutes to clean up the mess.

Metra and Amtrak officials were helping commuters heading to nearby platforms for the BNSF, Southwest Service and Heritage Corridor lines, Metra said in a service alert on its website.

This is the second pipe break to affect the South Concourse this week.

On Tuesday, the extremely low temperatures caused a sprinkler pipe to break, spilling dark-colored water on the floor near some platforms.

That incident had no impact on trains, but has promoted transit officials to modify pedestrian pathways at the station to lessen the amount of cold air coming into the station.

Starting immediately, the corridor connecting the North and South Concourses will be closed between 9 a.m. and 3 p.m. and between 8 p.m. and 5 a.m., Amtrak said Friday. That means people walking to the ticket offices for Amtrak, Metra and Greyhound or to and from Canal Street will be redirected.

The use of automatic doors and escalators between the east side of Canal Street and the concourse will also be limited in off-peak hours, Amtrak said.

Riders will not see any changes to the entrances at the Chicago River, and to and from Adams Street and Jackson Boulevard, the statement said.

The changes will stay in place through the end of February.