We live in a vigilant age that triggers the same question after every calamity: Was it a terror act? The passenger train derailment and fatal wreck Tuesday night in Philadelphia is no exception.

The answer appears to be no. Not this time.

Amtrak Train 188, with 238 passengers and five crew members aboard, jumped the tracks late Tuesday night and ended in a heap of twisted metal. At least seven people died and more than 200 were treated for injuries. The wreck closed the nation’s busiest rail corridor between Washington and New York as federal investigators begin sifting through the remains to determine what went wrong.

The FBI says there is no evidence uncovered so far to implicate any terror group or act. Preliminary findings indicate the train was traveling about 107 mph when in approached a curve with a speed limit of only 50.

However, the wreck draws attention to the possibility of an eventual terrorist attack on America’s rail system. Recent unrelated incidents draw attention to the system’s vulnerabilities in the wake of this man-made disaster.

The most immediate incident, and one of the most disturbing, is a report that another train on the same tracks came under attack about 20 minutes earlier just 3 1/2 miles away. The Philadelphia commuter train was hit by a projectile, breaking the windshield, according to the Southeastern Pennsylvania Transportation Authority. SEPTA spokeswoman Jerri Williams said they don’t know what the projectile was. There’s no indication the incident was related to the derailment. Nonetheless, it’s an uncanny coincidence.

Attacks on trains in the United States are rare, but they do happen.

In 1995, an Amtrak train derailed near Palo Verde, Ariz. The two locomotives and eight of the 12 cars derailed, four of them falling 30 feet off a trestle bridge into a dry river bed. One passenger died and 78 people were injured, 12 seriously. Investigators determined the rails had been sabotaged, and notes at the scene attributed the act to the “Sons of Gestapo.” There have been no arrests.

Since the 9-11 terror attacks, the FBI has issued alerts about the theft of devices used by railroads for derailing train cars. The alerts note that the devices, known as derailers, are possibly being stolen by terrorist groups intending to cause a train crash. Authorities said the thefts are baffling because they have no known use to anyone but the railroads.

An investigation continues into the January wreck of a CSX train in rural South Carolina. The FBI said the train intentionally was diverted down the wrong tracks before it collided with several rail cars parked on the siding. The conductor and engineer were injured. Damaged tank cars leaked 19,000 gallons of toxic hydrochloric acid. The FBI is offering a $10,000 reward for information leading to an arrest.

There is an ongoing quantum growth in rail operations. The U.S. freight rail network is widely considered one of the most dynamic freight systems in the world, with $60 billion generated annually over 140,000 rail miles by seven major railroads, about 20 regional railroads and 500 local railroads. Combined, they provide 221,000 jobs and move more freight than any other rail system worldwide.

Disruption of the rail system, particularly along its busiest routes, would alarm and affect many thousands of individuals and businesses, making trains and rails a natural target for terror operatives.

The Federal Railroad Administration is committed to maintaining a vibrant and safe rail system. Hundreds of millions of dollars each year is spent for rail system and train improvements. Tuesday night’s wreck demonstrates the ongoing need to do so.

And while there’s no evidence thus far that anyone caused the Philadelphia derailment, the notion of that knee-jerk question — was it a terror act? — should serve also as a reminder that security and vigilance must be considered part of a safe rail system.