Police with sniffer dogs are currently searching the Poppy Factory in Richmond.
Officers were called to the factory in Petersham Road shorly before 2pm after reports that two shoplifters had run into the building after fleeing a nearby shop.
One of the suspects is believed to have had a knife.
Police have cordoned off the factory and officers with sniffer dogs have been scouring the building.
A police spokesman said: "At the moment this is an ongoing investigation.
"So far one of the suspects has been detained and police have retrieved some of the property.
"We are still searching for the second suspect."
- Updates will be added to this story.
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 The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.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