BHP Billiton Iron Ore
The record was set on June 21, 2001 in western Australia between Newman and port headland, a distance of 275km (170 miles) and the train consisted of 682 loaded iron ore wagons and 8 GE AC6000 locomotives giving a gross weight of almost 100,000 tonnes and moved 82,262 tonnes of ore, the train was 7.353 km (4.568 miles)
BHP Billiton iron ore train has typically 268 cars and a train weight of 43,000 tonnes carrying 24,200 tonnes of iron ore, 2.8 km long, two SD70ACe locomotives at the head of the train and two remote controlled SD70ACe locomotives as mid-train helpers.
BHP Billiton used to run iron ore trains of 336 car length, 44,500 tonnes of iron ore, over 3 km long, six to eight locomotives including intermediate remote unit. This operation modes seems to be ceased once the trunk line was fully double tracked in May 2011.
The record-breaking ore train from the same company, 682 cars and 7,300 m long, once carried 82,000 metric tons of ore for a total weight of the train, largest in the world, of 99734 tonnes. It was driven by eight locomotives distributed along its length to keep the couplings loads and curve performance controllable.
source: Wikipedia and google