Train operator of NSW Trains said the train had hit a buffer at the end of the line at Richmond, about 65 km northwest of central Sydney.
NSW Fire & Rescue reported three people were trapped as a result of the collision. Emergency services are on the scene. Three helicopters, 17 ambulance crews, and fire and rescue teams were deployed to escort passengers off the train.
A meeting between representatives from rail operator Sydney Trains and the state's transport union, which had voted for a January 29 strike following failed negotiations over wage increases, was suspended following the incident on Monday morning, according to local media.
Witnesses have described a scene of chaos, with the train apparently hitting the buffer at the end of the line "at speed".
On social media witnesses described a "horrifying train crash", with "people injured everywhere".
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A total of 16 people, including the driver and two other staff members, were treated at the scene.
"My first thoughts are with those who have suffered some form of injury", he said.
A train accident at Richmond Station in Sydney's north-west has left at least 15 people injured.
He said it was "difficult" to say how fast the train was travelling when it hit a barrier. "Today's offer didn't provide that, so we've asked them to go back to the drawing board".
"Safety is our number one priority and we will now work to determine what caused the incident". He said the train did not appear to brake.
Salary negotiations between Sydney Trains and the Rail, Tram and Bus Union over pay conditions were halted when news of this morning's crash reached the meeting.