The Transportation Security Administration issued an advisory on Friday that a Piper PA 25 Pawnee crop-dusting aircraft was stolen from Ejido Queretaro, near Mexicali, Mexico, on Nov. 1. "Although there is currently no indication that this has any connection to terrorist activity," the TSA said, "the theft is cause for concern. Past information indicates that members of al-Qa'ida may have planned -- or may still be planning -- to disperse biological or chemical agents from cropdusting aircraft." The stolen aircraft is registered in Mexico and bears the tail number XBCYP. If you see the aircraft, the TSA says you should immediately contact the TSA General Aviation Hotline at (866) 427-3287. The TSA encouraged aerial-application operators and airport operators to take security measures such as storing aircraft in locked hangars with electronic security systems, parking airport heavy equipment such as trucks and forklifts where it would block aircraft access, use propeller locks and chains or tie-downs to secure aircraft stored outdoors, and more. Additional security guidelines are available from the TSA and the National Agricultural Aviation Association. The TSA added that any suspicious activity should be reported immediately to local law enforcement as well as to the TSA General Aviation Hotline at 866-GASECUR (866-427-3287).