Nine police officers have been injured after trying to shut down an illegal rave attended by thousands of people.
Missiles were launched at officers by punters at the unlicensed music event in a venue on Thames Road, Barking, on Saturday night, the Met Police said.
Four of those injured required hospital treatment and nine men were arrested at the disturbance.
Around 1,000 people were discovered outside the building after authorities were called at 9.45pm, with a further 1,000 revellers found inside.
It took several hours for the site to be cleared, police said, and the venue was emptied by 2am.
Road closures around the area will remain in place for the rest of Sunday and officers are still in place at the scene.
Temporary chief superintendent Sean Wilson said: "A number of officers were injured whilst going about their duties and this will not be tolerated.
"A full investigation has been launched and we will endeavour to bring those responsible to justice.
"We are working very closely with the community who are shocked by these events."