MINEOLA - Police across Long Island are on heightened alert as U.S. counterterrorism officials investigate what they are calling a specific and credible al-Qaida threat of car bombs on bridges and tunnels in New York City and Washington, D.C.

Residents who ride the rails and commute into the city are being warned to expect beefed-up security throughout the weekend. Officers began checking commuters' bags at Long Island Rail Road (LIRR) stations this morning.

Authorities have put extra officers on patrol, and have radiation detectors and other security measures in place. Rep. Peter King (R-Seaford) says all levels of law enforcement are checking out every possible lead and running it to the ground.

Last night at the Hicksville station, there was a scare after railroad officials thought there may have been an explosive device inside a car. The incident turned out to be a false alarm.

Local police say they will not only be on high alert this weekend, but will maintain increased security through the end of September when the U.N. General Assembly wraps up in the city. Officials probe terror threat ahead of 9/11 anniversary Police give all clear in Hicksville after bomb squad investigationOfficials chase unconfirmed al-Qaida bomb plot