Cam belt snapped

she sure the oil light started flashing before the car cut out? how long was the light flashing? this maybe a clue to why it broke!

24v? assuming its a v6 diesel then, what engine code?

cambelts can break in 2 ways for 5 different reasons
the 2 ways are;
1) the teeth themselves strip off the belt leaving the backing intact.
2) the backing itself breaks.
reasons for the belt breaking are usually.
1) its worn out/overdue for a change........ 7 times out of ten teeth strip off in this situation, the other three times the backing breaks.
2) a failure of a cambelt roller or water pump....... making the belt run out of line....... or component seizes up, generally rollers and waterpumps work on the backing side of the belt.
3) siezure of a camshaft in the head...... if the belts in good condition this will snap the backing. if its a bit worn already it'll strip the teeth.
4) a fluid leak into the belt area...... the fluid (oil/coolant) will breakdown the rubber components till it snaps.
5) failure of the tensioning system...... either letting the belt go completely slack to the point it lets the timing belt jump teeth. or its just not as tight as it should be, flapping about excentuating wear characteristics, belt fails before its time.

it is very odd if its a clean break on the belt and they cant see a reason for it. ie; non of the above.

hope this helps!