Play at the US Open had to be suspended when a drone crashed at the Louis Armstrong Stadium at Flushing Meadows yesterday.

The object flew into the court during Flavia Pennetta's 6-1 6-4 win over Monica Niculescu, crashing into a flight of stairs in the stands.

A statement from the USTA said: "No spectators were in the immediate area of the crash and there were no injuries. The NYPD responded and is conducting an ongoing investigation."

Meanwhile, Pennetta told reporters: "I was a little bit scared, I have to say. With all the things that happen now in the world, I'm imagining 'okay, it's a bomb.' That was my first reaction. I think it's normal to think something like that. I was trying to keep playing. I saw the police there watching and everything."

The unmanned aerial devices have become popular with photographers in recent years, but can also be used for military purposes, surveying and crop spraying.