If a strange object is seen hovering over a stadium during an important match, many may mistake it for a UFO (unidentified flying object), a spying device or even a bomb. The same happened at the Louis Armstrong Stadium during the ongoing US Open Championship on Thursday evening.

The incident took place during the match between 26th-seeded Flavia Pennetta of Italy and Monica Niculescu of Romania in which the former won 6-1, 6-4.

The strange object that buzzed over the stadium and briefly interrupted the match turned out to be just a drone and not a UFO or any dangerous object that many might have suspected. Luckily, it crashed into some empty seats at the stadium having the capacity to accommodate 10,000 spectators.

Later, the US Tennis Association (USTA) said in a statement that the drone did not hurt anyone as it crashed into an empty area. The New York Police Department is investigating the matter, it added.

Pennetta, who beat Niculescu to advance to the next round, said that she was scared and initially thought the object could be a bomb.

"A little bit scary, I have to say," Pennetta told ESPN. "With everything going on in the world ... I thought, 'OK, it's over.' That's how things happen." 

She went on to say that she was left in the dark about the incident as neither the chair umpire nor tournament officials told her what it was.

"All of these [security measures], and then it comes in from above," Pennetta said. "If there had been spectators, it would have hit them and done a lot of damage."