The National Transportation Safety Board will issue a report and recommendations after investigators determine what caused an Angels Flight car to derail, stranding six passengers.
In the meantime the funicular, the shortest railway in the world at 298 feet, could be shut down for months while federal officials investigate Thursday's incident in downtown Los Angeles.
The car called Sinai derailed and left one passenger stuck at the lower end of the track. Five passengers on the other car, Olivet, which was near the top of the railway, were assisted off shortly after the incident. No one was injured.
Dave Watson, a senior railroad accident investigator with the National Transportation Safety Board, said officials from the California Public Utilities Commission and Angels Flight Railway President John Welborne spent Monday afternoon inspecting the equipment, running tests on the stalled trolley and gathering documentation.
Video cameras installed on the system show Sinai descending the hill, derailing at the bottom and maneuvering before it was pulled back up the track, Watson said.
"We got some insights but didn't really come to a probable cause," he said.
Officials hope to have representatives from the company that manufactured the funicular's complex system fly in for further testing later this week, he said.
Welborne said the fix probably won't be expensive and he doesn't foresee any major trouble. He's hoping it will reopen sooner than anticipated.
Angels Flight carries passengers up and down a steep incline between Hill and Olive streets. The tiny rail line originally opened in 1901, operating alongside the 3rd Street tunnel until 1969, when it was shut down because of a lack of ridership. It reopened in 1996 in a different location.
The railway was shut down after a fatal accident in 2001 that killed an 83-year-old passenger and injured seven others when the brakes on Sinai failed, sending it crashing into Olivet.
Federal investigators concluded that faulty mechanical and brake systems, combined with weak oversight, led to the crash.
The railway was rebuilt entirely in 2009, with several layers of safety systems to prevent such accidents. After the $3.5-million overhaul, the funicular reopened in March 2010.
It was briefly shut down in June 2010 after a car was seen operating with an open gate and again in 2011 because of wheel deterioration. Inspectors for the California Public Utilities Commission discovered damage to the flanges — which hold the cars' wheels on the rails — during a routine inspection. Angels Flight reopened shortly thereafter when safety inspectors signed off on repairs.