Police officers were called to the scene of a fight and reports of a man with a knife on Yiewsley High Street - but found no victims or suspects when they arrived.
The first call was made to police shortly after 8pm, on Wednesday (May 23) evening, when officers were told that a large fight between a number of men had broken out just outside Yiewsley Library.
One man was reportedly armed with a knife, but there have not been any reports of serious injury as yet.
Residents reported hearing a helicopter overhead on social media around two hours after the alleged incident.
A Met Police Spokeswoman said: "Police were called to High Street, Yiewsley at 8.07pm on Wednesday (May 23) to reports of two or three males armed with weapons fighting in the street.
"Officers attended and conducted an extensive search of the area. No victims or suspects were traced and there was no indication that any persons had been injured.
"Officers from Hillingdon investigate. Enquiries continue."
The London Ambulance Service have been contacted for comment, and we will update with any further news when it comes in.