Twenty-two of 33 freight cars that were headed south on Union Pacific's Fresno subdivision line somehow slipped off the tracks on a small trestle bridge at Dillard Road in South Sacramento.
The three employees on board managed to escaped the crash without being hurt.
"Were there hazardous materials spilling into the waterway or is there going to be a vapor cloud of some sort that's going to affect a lot of people?" strategized Julie Rider with the Cosumnes Fire Department.
Those were some of the first concerns for crews from her department who were first on scene.
While there were no hazardous materials on board, it was still a hazmat situation as fuel leaked into the river along with some type of food product that the train was trying to take from Tracy to Roseville, possibly tomato paste.
"All of our operating folks, Union Pacific, police, local municipalities, will work to get this cleaned up as quickly and as safely as possible," said Justin Jacobs with Union Pacific.
Union Pacific tells FOX40 that the tracks are checked at least twice a week, and more frequently during weather events.
The region has endured multiple rounds of flooding rains just this week.
It's not yet known if an inspection done by the railroad just yesterday missed something or if the rising floodwaters right under the trestle degraded it enough in as little as 24 hours to push the train into taking a plunge.
In 2014 California became the first state in the country to task a state agency, the Public Utilities Commission, to inspect private rail bridges.
The CPUC has yet to confirm the timing or results of its last assessment there.
The rising Cosumnes River prompted Union Pacific to call off its investigation and removal efforts Friday night.
The railroad plans to resume work at the crash site at daybreak Saturday.
Amtrak shares the tracks involved in the accident with Union Pacific.
Spokesmen tell FOX40 their trains have been rerouted to other lines and that no passengers were delayed.
Stay with FOX40 and FOX40.com for the latest information on this developing story.