LOS ANGELES — Trains on Metro’s Blue and Expo lines could be very crowded this morning due to fallout from a mishap at the Blue Line rail yard, officials said.

The Metro Blue and Expo line trains will consist of two cars instead of the usual three while crews repair power system damage from a train derailment Sunday in the Blue Line yard, said Metro spokeswoman Kimberly Upton.

“There were no passengers onboard the train when the incident occurred as the train had not yet gone into service,” Upton said.

She urged passengers to prepare for crowded conditions on the two rail lines by boarding at the front or center of platforms and allowing extra travel time.

“Some may want to consider a combination of the Green Line and Silver Line between downtown and South Los Angeles to avoid potential delays and overcrowding,” Upton said.

Trains are scheduled to run every six minutes during rush hour and every 12 minutes during midday, she said.