Police have been forced to close roads in Adelaide this morning after two freight trains collided in Adelaide's inner south-west causing the derailment of several carriages.

Two level crossings are now blocked south of the scene at Keswick as authorities work to clear the track.

It is understood one freight train collided with the rear of another which caused a train passing through the crossings while the boom gates were down to become blocked.

Level crossings have been closed south of the crash. (Twitter @alicemonfries)

This image might provide some clues.I would guess the SCT 2MP9 has hit the back of the wagons in front.Read more at http://www.9news.com.au/national/2015/03/31/09/46/freight-train-collision-blocks-level-crossings-in-adelaide#drm67RBZytyuYSwR.99