| A computer-generated file image shows the Olympic stadium after completion, after it was unveiled in London. [Photo/Agencies]

LONDON - The security firm protecting London's Olympic Park ordered an internal investigation and began disciplinary procedures on Thursday after two guards were arrested on suspicion of possessing explosives.

The probe followed the arrest of a 40-year-old woman, also charged with suspected possession of drugs, near the Olympic complex on Tuesday and a 43-year-old man at his home in Wales a day later.

Police said in a statement that the woman, a dog handler for private security firm G4S whose car was stopped and searched, had been bailed to return to an east London police station in late April.

The man was being held at an east London police station but police said the arrests were "not terrorist related".

Media reports said the explosives were believed to be Semtex.

G4S, who have signed a contract worth at least 100 million pounds ($161 million) as the Games' official security services provider, said in a statement they were assisting police with enquiries.

"G4S take breach of operational processes very seriously," said the company, which is listed in the FTSE 100.

Officer Suspended

It has said it will recruit, train and manage the 10,000 guards needed for the Games.

"An internal investigation has been launched and disciplinary procedures instigated, which has resulted in the suspension of one officer, pending the outcome of a police investigation.

"An investigation has also been launched into the alleged conduct of a second officer."

The security firm said its dog handling team were licensed to hold small samples of explosives and controlled substances for training purposes but were required to follow "strict operational processes".

"All dog handlers are fully vetted and operate to the highest industry standards," it added.

The Olympic Delivery Authority responsible for building the facilities said there had been no change in the level of security at the Park after the arrests.

"Robust measures are in place to ensure the safety and security of the Olympic Park including person and vehicle screening," a spokesman said.

"Work has continued as normal and there has been no risk to the safety or security of the Olympic Park."

Britain plans an intensive security operation to guard the Olympics. The country's role in the wars in Iraq and Afghanistan has increased the threat posed by Islamic militants.