A large grass fire across the GO Train tracks south of Newmarket, Ont. forced Metrolinx to halt service to Barrie during rush hour.

The northbound tracks were shut down for nearly two hours due to a fire at Mulock GO crossing, Metrolinx says.

The fire started near Mulock Drive and Bayview Avenue.

According to York Regional Police, the flames spread, making visibility in the area poor due to heavy smoke.

Fire crews were able to get the blaze under control around 6 p.m.

GO Train service on the Barrie line interupted three trains, which were held at Union station, Anne Marie Aikins, a spokesperson for Metrolinx told CP24.

The trains have since began to move, but Aikins warns commuters to expect delays.

No injuries have been reported.