LONDON, March 31 (UPI) -- Police arrested a female security guard at London's Olympic Stadium site on suspicion she possessed a small amount of explosives, officials said.
It was unclear what kind or how much explosives the woman allegedly had, Sky News reported Thursday.
The 40-year-old woman was being held at an east London police station. She also allegedly had illegal drugs in her possession.
Investigators said she works for the security firm G4S, ostensibly as a dog handler.
Investigators said the amount of explosive recovered was "very small" and the incident is not being treated as terrorist-related. A source told Sky News the firm's dog handlers may legally possess a small amount of explosives to use in the training of their animals.
"G4S take breach of operational processes very seriously and are assisting the police with their inquiries in relation to this incident," the woman's employer said.
The incident occurred Tuesday. London will host the Summer 2012 Olympics.
"Work has continued as normal and there has been no risk to the safety or security of the Olympic Park," the Olympic Delivery Authority said in a statement.