That means tighter security on rail lines everywhere. An alert to law enforcement officials in all 50 states has been sent out.
Mass transit has remained a target. It is the most vulnerable, according to Homeland Security officials and has been the focus of numerous terrorist plots in the U.S.
In 2007, several railroad spikes were removed from the tracks used by Metra's Electric and South Shore lines. Despite a $50,000 reward, the FBI has not found those responsible.
"It is still an active case. Fortunately, we haven't had any other circumstances like this since then, and we will continue to be very vigilant in surveying all of our property," said Judy Pardonnet, Metra spokesperson.
The response to the information, from our federal government, in part: