MONTICELLO - Crews worked through Thursday night and into Friday repairing the railroad tracks on the south side of Monticello where a freight train derailed early Thursday morning. Norfolk Southern Corp. is investigating the cause of the derailment, which interrupted power to about 1,900 customers in Monticello and nearby communities.

Rudy Husband, Norfolk Southern spokesman, said the company is examining the condition of the track at the time of the accident, the condition of the train and how the train was being handled.

The engine's data recorder will reveal the speed at which the train was traveling. The speed limit at that point is 50 mph.

There were no injuries in the accident, which occurred in a mixed-use area containing industrial plants and homes. The train, which had 28 freight cars and two locomotives, carried two crew members.

Several of the derailed cars crashed into power poles carrying transmission lines, causing the outages, which lasted about 3¼ hours for some of the AmerenIP customers.

Some of the empty grain cars still rested on their sides at the edge of a farm field Friday afternoon, just west of the railroad embankment. A company specializing in railroad emergencies had cleared away the cars that blocked the tracks.

Rain and mud slowed the recovery effort Friday.

The railroad is required to file a report on the cause of the accident by Jan. 30.

Warren Flatau, Federal Railroad Administration spokesman, said most derailments are caused by track conditions. Other factors, such as the speed of the train, could play a role.

"Typically, railroads set their timetable at just under the permissible track speed," Flatau said.

The administration received word of the derailment early Thursday and decided not to perform its own investigation at this time, Flatau said. An investigation could be conducted later, depending on the report filed by the railroad, he said.

Flatau said railroads are required to inspect tracks regularly, with different guidelines depending on the loads carried and whether the tracks run through rural or urban settings. In many cases, companies will inspect tracks more regularly than guidelines mandate.

Husband said Norfolk Southern has been inspecting the Monticello track at least twice each week.