Red Line passengers in Cambridge will face a slower ride Thursday after a safety inspection discovered a “defect” in a section of curving track south of the Harvard Square station, according to the MBTA.

As a safety precaution, trains traveling between Harvard Square and Central Square will leave the station at 3 miles to 5 miles an hour as opposed to the usual 10 miles an hour, T spokesman Joseph Pesaturo wrote in an e-mail.

The T is in the process of manufacturing a replacement section of rail, he wrote.

“The defect is on a curve and a new section of rail will need to be manufactured by T workers today. It will be replaced tonight,’’ he wrote. “The MBTA apologizes to its Red Line customers whose commutes are being impacted.”


In a tweet, the T warned passengers they face a 15-minute delay in both directions.

The T first tweeted about the slowdown around 7:29 a.m., although service began around 5 a.m. The speed reductions did not impact early morning trains because fewer run at the time.

John R. Ellement can be reached at ellement@globe.com. Follow him on Twitter @JREbosglobe.