Police were seen searching forest close to Woodford New Road in South Woodford this morning.
A police helicopter has also been seen hovering over the area and witnesses have reported several police vehicles on nearby Chelmsford Road.
One man, who did not want to be named, said: "I saw dozens of police up near the Napier Arms pub at around 10.45am.
"There were some with dogs and a lot of cars."
Another said he had seen police chasing someone into the forest.
The Guardian spoke to an officer on Chelmsford Road who was not prepared to comment.
Redbridge police have been asked for an update.
Did you see what happened? Call Dominic Sutton on 07795 316 211.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here