Thomas Tuchel has arrived at the Stade Louis II
Police are said to have stopped the bus on its route to the stadium and kick off has been delayed by five minutes.
The players are now at the ground and have begun warming up, but police have stepped up their security after last week's attacks.
"The police read our team bus for approximately 20 minutes without justification not by the hotel exit," Dortmund tweeted.
— Borussia Dortmund (@BVB) April 19, 2017
Marc Bartra: Dortmund stars show support for defender against Monaco Wed, April 12, 2017
Click to reveal the best snaps of Marc Bartra tributes during Dortmund v Monaco
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Click for the best snaps of Marc Bartra tributes during Dortmund v Monaco
The Dortmund bus was hit by explosions on their way to the stadium last week, with Marc Bartra sustaining a wrist injury.
Dortmund went on to lose 3-2 to Monaco after the game was postponed for 24 hours.
Thomas Tuchel criticised UEFA for making them play so soon after the attacks and Nuri Sahin gave an emotional interview saying no one's mind was on the match.
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