Stabbing Reported at Bono's Hollywood Hills Investment Property

A Hollywood Hills property Bono's invested in was visited by first responders Thursday ... after authorities received a call about an alleged stabbing, TMZ has learned.

The Los Angeles Police Department tells TMZ officers responded to the stabbing report around 1:20 PM PT, and they immediately started investigating the claim.

The Los Angeles Fire Department tells TMZ they dispatched one fire engine and one ambulance to the house for an unconfirmed but reported stabbing ... and, we've obtained video of a helicopter circling the area while an ambulance climbed up the hill to the home.

We don't know the exact details of the incident, but we're told the property is still considered a construction site -- and, we've heard only construction workers were supposed to be at the property today.

We also know Bono is currently out of the country, and he's not involved in this situation whatsoever

Sources familiar with the situation tell TMZ ... the house is for sale, though it's not listed publicly -- we're told people in the real estate industry know it's being shown off-market. Our sources also say Bono is just one of many investors in the property.

We've reached out to Bono's team ... so far, no word back.