Union Pacific says the timeline for repairs at the site of Monday’s train derailment in northeast Iowa is unknown.

Forty-four Union Pacific train cars derailed on and around a railroad bridge north of Hampton. A statement from the company indicates most of the cars have been removed from the track and crews have started to repair the track and the bridge.

Hazardous materials crews are back at the site today, removing asphalt that spilled from the train into Otter Creek.

The cause of the derailment is still under investigation according to Union Pacific. No one on the crew was injured when the train’s cars started leaving the track at about 3:30 Monday morning.