9 August 2004 Hundreds Evacuated After Sask. Train Derailment Hundreds of residents of Estevan, Saskatchewan are waiting to return to their homes after being evacuated in the wake of a train derailment.   Six cars derailed and another three tipped over as the train was backing up Sunday afternoon.   The 84-car train was carrying anhydrous ammonia, a potentially-fatal component of liquid fertilizer.   Officials say none of the cars appear to be leaking, and Estevan fire Chief Rick Perry told reporters there was "no immediate threat to life or property".   Homes and businesses - including a seniors' home - within a three block radius of the derailment were evacuated.   Representatives from Canadian Pacific Railway and crews from Saskatoon headed to Estevan Sunday to assist with the cleanup effort.   It is unclear when residents will be allowed to return home.