People exiting the train at Sirocco station told CBC News that two people were escorted from the train by the police tactical team and one man was handcuffed.
They said there were still people inside the train.
Calgary police responded to a call around 1:40 p.m., a police spokesperson told CBC News.
Police at the scene described the situation as dangerous and declined to comment further.
The officers were cleaning the cars.
The west line of the LRT has been shut down.