Light rail services across Sydney’s CBD and eastern suburbs have been suspended after two trams were involved in separate fire-related incidents.

The L2 Randwick and L3 Kingsford lines between Circular Quay, Randwick and Juniors Kingsford were suspended on Saturday after smoke was detected on the roof of two light rail vehicles.

Smoke was first reported about 7.55am between Wynyard and the QVB in the CBD, before a second incident about 10.25am near South Dowling St in Surry Hills.

Know the news with the 7NEWS app: Download today

In both cases, passengers and drivers safely disembarked and no injuries were reported.

Operator Transdev said the L2 Randwick and L3 Kingsford lines had been suspended as a precaution while it worked with Transport for NSW and relevant safety authorities to complete a thorough risk assessment before services resume.

Replacement buses are operating between Central and Randwick and between Central and Juniors Kingsford, while L1 Dulwich Hill Line services continue to operate as normal.

“The safety of passengers and employees is our highest priority,” a Transdev spokesperson said.

“We understand this disruption is frustrating for customers and appreciate their patience.”

Transport for NSW has urged passengers to use alternative transport where possible and allow extra travel time.

South Dowling St was reopened to northbound traffic after the affected light rail vehicle was removed.

The incidents come after another light rail vehicle caught fire earlier this month, making Saturday’s events the third fire-related incident involving Sydney’s light rail network in the past fortnight.