Russia has been jamming U.S. drones in Syria, blocking GPS signals and causing them to malfunction, according to officials. Four U.S. officials told NBC News that the Russians had been crippling American drones for the past few weeks, seriously affecting military operations. The officials said they believe the Kremlin became concerned the U.S. would retaliate for a series of suspected chemical attacks in the country and began interfering with drones operating over the skies of Syria, jamming blocks or scrambling a drone’s reception of a satellite signal, which can cause them to malfunction or even crash. Officials said the drones affected so far are small surveillance aircraft, as opposed to larger Predator and Reaper drones that operate in combat environments and can be armed.