A two-foot quadcopter drone crash landed on the lawn of the White House early Monday morning. Although the Secret Service said the drone was not a security threat, the crash resulted in an immediate lockdown of White House grounds while officials examined the craft and searched the grounds. It is not known where the drone came from.

According to the Secret Service, the drone was a two-foot quadcopter, an unmanned aircraft flown by four propellers. It crashed on the southeast side of the White House at about 3 a.m. Emergency vehicles, including police and fire, rushed to the White House. Once daylight came, Secret Service officials searched the lawn and large bushes lining the driveway.

The incident is yet another in recent security breaches at the White House that have led to questions of the Secret Service’s effectiveness, and the reassignment of four high-ranking executives. There is a three-mile no-fly zone around the White House that affects all pilots as well as unmanned drones, but that has been violated by small unmanned aircraft in the past. On July 3, Secret Service patrols detained an individual who was flying a quadcopter drone similar to the one in today’s crash, about one block from the White House grounds. The Secret Service did not identify the pilot or release whether charges were filed, but they did confiscate the drone. On July 7 another person was questioned after flying a quadcopter drone near the Lincoln Memorial.

On Aug. 19 an unidentified man was arrested after being found by District police stuck in a tree, where he had climbed to retrieve a small drone that had been caught in the branches.  On Aug. 29, U.S. Capitol Police detained an individual for flying a drone on Capitol grounds.

Quadcopters have been linked to smuggling, including a failed attempt to transport drugs into a Dublin prison last year. A quadcopter carrying 6.6 pounds of meth crashed into a San Ysidro, Calif., supermarket parking lot last week, suspected to be coming from Mexican drug traffickers.

Today’s incident comes at a time when the Federal Aviation Administration (FAA) is developing rules for unmanned aircraft, as ordered by Congress in 2012. Problems are occurring in increasing numbers as these popular drones share the skies with passenger aircraft. The FAA reports nearly 200 drone incidents between last February and November, as the small planes were flown near other aircraft or restricted areas.

Although essentially sophisticated toys, quadcopters have commercial uses for aerial inspections and photography. They were popular Christmas gifts last year, weighing only a few pounds and costing only a few hundred dollars.

The president and Mrs. Obama, who are traveling in India when the incident occurred, were not at the White House. It is not clear whether daughters, Sasha and Malia, were at home. An investigation is under way to determine the source of the aircraft and any possible motive, as well as identify suspects.