Workers have secured a tree fallen on train tracks at Park Road station, allowing services to resume.

The tree was blocking tracks between Park Road and South Bank stations, causing long delays.

A Queensland Rail spokeswoman said the tree would be completely removed later in the day when it wouldn't impact services.

Twenty-minute delays remain on the Beenleigh, Gold Coast, Airport, Ferny Grove, Shorncliffe and Cleveland lines but Queensland Rails said they would ease for the afternoon peak.

"We apologise to our customers for any disruption to their service and thank them for their understanding," she said.

Update 2.15pm

Trains have resumed on the Beenleigh, Gold Coast, Airport, Ferny Grove, Shorncliffe and Cleveland lines as Queensland Rail staff work to clear a fallen tree blocking tracks at Park Road.

Some trains are still being diverted via the Tennyson loop with customers warned to expect delays of up to 35 minutes.

A Queensland Rail spokeswoman said crews were onsite and working to remove the tree "as quickly and safely as possible".

"We apologise to our customers and thank them for their understanding," she said.

Earlier

A tree has fallen across train tracks, cutting off services on more than half of the Brisbane's train lines.

Trains are suspended in both directions between Park Road and South Bank stations due to the fall at Park Road, affecting the Beenleigh, Gold Coast, Airport, Ferny Grove, Shorncliffe and Cleveland lines.

Translink is warning of hour-long delays to passengers.

Beenleigh, Gold Coast and Cleveland line trains are being diverted via the Tennyson loop to take passengers to and from the CBD.

Translink is arranging transport between Roma Street and South Bank stations.