School is back in session for Fairfax County Public School students — but they may be later than the two-hour delay Friday morning.

FCPS officials said Friday morning that the system is experiencing significant delays as buses try to warm up in the single-digit temperatures after being idle for the entire week. Students were off for Martin Luther King Jr. Day on Monday, and then for three straight snow days, which drew criticism from many residents.

From FCPS:

FCPS is experiencing significant mechanical problems with some buses across the county this morning due to the freezing temperatures.  Some of these buses will be late picking up students; some may be very late.  Parents are advised to take precautions to ensure that their children are not standing outside in the cold for extended periods of time.  Mechanics, transportation supervisors, and drivers are working to the best of their ability to get the buses running and on time.

Thank you for your patience and understanding, and we apologize for the delays.

At-large school board member Ryan McElveen said earlier this week that mechanical issues were part of the consideration in canceling school this week, even as road conditions improved.