A mystery drone interrupted the US Open on Thursday as it flew over the court in Louis Armstrong Stadium and crashed into a section of empty seats.
The flying object entered the arena towards the end of Flavia Pennetta's 6-1 6-4 win over Monica Niculescu and play had to be temporarily suspended while security examined the device.
A USTA statement read: "No spectators were in the immediate area of the crash and there were no injuries.
"The NYPD responded and is conducting an ongoing investigation."
Pennetta admitted she had been unnerved by the drone's arrival.
"I was a little bit scared, I have to say," Pennetta said.
"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."
Play eventually continued while police continued to inspect the device and Pennetta recovered her focus to book her place in the third round.
Joining the Italian is 20th seed Victoria Azarenka, who has twice been a runner-up at Flushing Meadows but is yet to add the title to her two grand slam triumphs.
Azarenka was made to work hard for her 7-5 6-4 victory over Belgian Yanina Wickmayer and will now face 11th seed Angelique Kerber, who beat Karin Knapp in straight sets.
"It is going to be a very tough match," Azarenka said.
"She's an amazing fighter and sometimes you feel like you're playing against the wall.
"I have to find a lot of ways to get her off balance and to be aggressive and try to find empty space in the court.
"But she's an amazing player. She's been really solid throughout the year, so I'm looking forward to having this battle and to test myself and try to find a way to win."
Azarenka is due to meet second seed Simona Halep in the quarter-finals and the Romanian also progressed after a comfortable win over Ukraine's Kateryna Bondarenko.
Halep's victory was not a surprise but the world number two has been turning heads off the court, after she rode the tournament bus to Flushing Meadows rather than her own private transport.
Riding with journalists, coaches and tournament staff, Halep had a simple explanation for her choice of travel: "Because I prefer bus."
Source: PA
