Periodic testing of the Devon Bridge between Milford and Stratford Sunday could cause delays on Metro-North.

The testing, which was scheduled to start around 8 a.m., may require periodic openings, according to Metro-North. Any openings could cause delays of 20 to 25 minutes.

An opening of the Cos Cob Bridge in Greenwich scheduled for 11 a.m. could also cause 20- to 25-minute delays.

Metro-North said it will issue updates throughout the day.