Investigators will consider storm-related flooding to help determine what caused an April 24 freight train derailment in North Texas that sent 25 tanker cars off the tracks.
The National Transportation Safety Board on Monday issued a preliminary report on the accident south of downtown Fort Worth.
Officials say at least three horses were killed and several Texas homes had to be evacuated when the Union Pacific train hauling flammable liquid ethanol derailed and caught fire.
The NTSB statement says the derailment happened amid heavy rainfall and a large amount of water from nearby Lake Echo flowed through the railroad right of way.
Safety issues to be reviewed include effective weather alert communications and inspection and maintenance of storm water drainage from lakes.
Union Pacific is based in Omaha, Nebraska.