A pack of youths chased two others through central Hammersmith in a violent brawl believed to be linked to a 16 th birthday party.
A 10 inch kitchen knife and a blood-soaked trainer were discovered in the aftermath of the altercation, which happened around King Street on the night that the nearby Emerald Centre had been hired out for the celebration.
Concerns were this week raised by police after it emerged the fight was the fourth serious incident linked to young people who have hired out the Beadon Road venue, with groups of uninvited youths believed to have been heading to Hammersmith from other parts of London intent on causing trouble.
Around 25 young people were involved in the chase down King Street, which happened just before midnight on February 5.
One youth was then seen discarding a serrated knife next to a bin outside the TK Maxx store, and man's trainer and a tissue both soaked in blood were later found close to the Emerald.
It follows three similar incidents over the last five years near the community building, which is operated by Hammersmith Community Trust.
One one occasion a blank gun was fired and knives and a broken pool cue were discovered in surrounding streets.
Inspector Tony Hirst, of Hammersmith safer neighbourhoods team, said: "Incidents of violence are few and far between over the last four or five years, but the concern is the potential severity of those incidents.
"Each time, the consistent pattern is that it has been a party for young people. My concern is that the centre is attracting people who aren't invited.
"It may be that they are getting wind of the parties and turning up, and there are therefore groups from different areas who are in conflict.
"When you have groups of youths rampaging around wanting to fight each other, it's more by luck than judgment that a serious incident doesn't happen."
The venue is yards from where 16-year-old schoolboy Kodjo Yenga was stabbed to death in 2007.
Chris Tranchell, a member of Hammersmith Community Trust, said he would work with officers to address any concerns about the venue, but that hundreds of events are routinely held there without a problem.
"This incident certainly didn't happen inside the Emerald or even in the car park," he said.