Metro’s Red Line was experiencing significant delays Wednesday morning after crews discovered a crack in the system’s electrified third rail.

Metro officials became aware of the cracked rail between the NoMa-Gallaudet and Rhode Island Avenue stations at about 6 a.m., just as the morning rush was starting. Trains were single-tracking between the NoMa and Fort Totten stations until about 7:50 a.m., Metro spokesman Philip Stewart said.