Two U.S. trains slipped off their routes on Thursday, two days after a deadly Amtrak accident near Philadelphia, according to reports.
Parts of a freight train derailed in Pittsburgh on Thursday morning, leaving some cars overturned or detached from their wheels, according to local station WPXI. No injuries were immediately reported.
A minor derailment also took place in South Carolina with no injuries reported, according to Georgia outlet WRDW. The engine compartment of another Amtrak train caught fire in Milwaukee on Thursday afternoon, though no passengers were hurt.
The incidents come as the Philadelphia accident—which left eight people dead and more than 200 injured—places scrutiny on the state of America's infrastructure and railroads.
"If we are going to have safe transportation systems in America, you have to invest in them. You have to keep up with state-of-the-art infrastructure," former U.S. Secretary of Transportation Ray LaHood said in an interview with CNBC's "Power Lunch" on Wednesday.
Read MoreAmerica in infrastructure crisis: Ray LaHood
"We haven't done that," he added.
National Transportation Safety Board investigators determined the Amtrak train was traveling at more than 100 mph—twice the area's speed limit—before it derailed while rounding a sharp curve Tuesday. The train may not have crashed if the stretch of rail had a congressionally-mandated pace control, NTSB board member Robert Sumwalt said Wednesday.
However, the NTSB stressed it could not yet conclude speed alone caused the accident.
Read MoreNTSB: Derailed Amtrak train was traveling more than 100 mph
LaHood on Wednesday called U.S. infrastructure—including roads and bridges—a "limp along, go along" system that Congress has a difficult time funding.
On Wednesday, the House Appropriations Committee voted in favor of transportation infrastructure legislation that would cut Amtrak funding by $252 million in fiscal 2016.
House Speaker John Boehner, R-Ohio, on Thursday dismissed claims that a lack of Amtrak funding could have played a role in the crash.
— Reuters contributed to this report