UPDATE, 2.30pm: Train services have returned to normal on the Joondalup line.
TRAINS are delayed on the Joondalup line between Leederville and Whitfords stations.
Transperth advised of the delay at 11.40am and attributed the problem to a technical issue.
Trains are running but will operate on a 30-minute frequency.
Passengers should allow extra travelling time and be aware services may not connect with timetabled bus and trains.