Police are trying to identify organisers of an illegal rave being advertised on social media for this weekend.
More than 500 people said they are going to the event at 8pm on Wandsworth Common tomorrow night via events site Pievents.
Police said they are working with the council and landowners to do all they can to prevent the rave from going ahead.
Newham borough commander Simon Letchford said: "Parties of this nature are not licensed, and they are often dangerous.
"No security staff, no medics, no concerns about the number of people present and unsafe properties all add up to a really dangerous place for people to be.
"People who live near these suggested venues shouldn’t have to tolerate the associated noise, crime and anti-social behaviour that can come with such raves."
Police said there will be an operation in force to protect Wandsworth over the weekend and officers will be visiting local properties to advise landowners on security.
Officers are also aware of an illegal rave planned in Erith, Newham, this weekend.
A police spokesman said: "Anyone who has any concerns or any information about the people responsible for planning these events should contact us on 101."