One dead, another injured in horror truck crash on Sydney's M1

A man has died and another remains in hospital following a horror truck crash in Sydney's north overnight.

Emergency services were called to the M1 at Wahroonga in Sydney’s North, in the southbound lanes, following reports of a crash at 10:40pm.

Crews worked to free a driver trapped in a truck on its side.

He was taken by ambulance to Royal North Shore Hospital suffering injuries in a stable condition.

A second truck was found down an embankment with the driver of that B-double suffering fatal injuries.

Chief Inspector Frank Gilmore  urged any drivers with dashcam or witnesses to the accident to come forward.

"Once emergency services got down to that B-double truck, he was located deceased," Chief Inspector Gilmore said.

"Initial investigations to this stage indicate that the B-double collided with the rear of the Pantek truck."

Motorists travelling southbound on the M1 Pacific Motorway between the Central Coast and Sydney experienced significant delays following the accident.

Two of three southbound lanes which were closed earlier today are now re-opened.

However motorists have been urged to allow extra time for their journeys.

Two southbound lanes are now open on the M1 past Ku-Ring-Gai Chase Road and one southbound lane remains closed on the motorway as the salvage operation continues.

Southbound traffic remains heavy on the M1 between Berowra and Asquith. 

Anyone with information about this incident is urged to contact Crime Stoppers: 1800 333 000 or https://nsw.crimestoppers.com.au.