The Secret Service is conducting middle-of-the-night drone flights near the White House in secret tests to devise a defense against the unmanned aircraft, the Associated Press reported Tuesday, citing an unnamed U.S. official. The government-controlled drones will be flown between 1 a.m. and 4 a.m. during the next several weeks over parts of Washington — airspace that's usually off limits as a no-fly zone, according to the official, who has been briefed on the plans. The official said the Secret Service is testing drones for its use in law enforcement and protection, and to identify how to defend against hostile drones. The official spoke to the AP on condition of anonymity because this person was not authorized to publicly discuss the plans. The Secret Service says details are classified. Among the tests is the use of signal-jamming technology to thwart control of a remotely piloted aircraft, the official said. Researchers at the Homeland Security Department, which oversees the Secret Service, have been testing methods to combat drones at remote sites. But testing in a real-world environment around the White House will help understanding of how radio waves are affected by buildings, monuments and even tall trees. The challenge for the Secret Service is how to quickly detect a rogue drone flying near the White House or another location where the president is, then within moments to either hack its guidance mechanism to seize control, or jam its signal to send it off course or make it crash. Some consumer-level drones, which often carry video cameras, have enough lifting power to carry small amounts of explosives. The Secret Service has said only that it will openly test drones over Washington, but it has declined to provide details.In January, a wayward quadcopter drone piloted by an off-duty U.S. intelligence employee landed on the White House lawn. The Secret Service said the landing appeared to be accidental and not a security threat.