WASHINGTON: An employee of a US spy agency has confessed to operating a small drone that crashed on the grounds of the White House, the agency said on Tuesday, the latest in a series of incidents that raised questions about the president's security.

A spokesman for the National Geospatial Intelligence Agency (NGA) said that an off-duty employee had told the US Secret Service, which guards the presidential mansion, that he had been flying the four-propellor drone when it crashed on Monday.

Read: Small drone crashes at White House complex, prompts lockdown

The NGA is a Defense Department agency whose principal job is to analyse photographs taken by spy planes and satellites.

The spokesman said that the Secret Service was investigating and at this point the man was not facing disciplinary action.

It did not name the employee or explain why he was operating the device near the president's home.

A Secret Service spokesman said the device, which set off an alert and a lockdown at the White House, was used for recreational purposes and did not appear dangerous.