Authorities in London arrested six possible terrorists -- subduing one with a stun-gun -- as part of a months-long international terror probe.
The investigation that prompted today's arrests by armed police has so far revealed no known connection to the Olympic Games set to begin later this month, although several arrests occurred near the main Olympic venue in London, according to a police statement and intelligence sources.
Separately, as the searches occurred today, police near Birmingham stopped a budget intercity bus after a passenger spotted a man pouring something into his bag and then saw smoke coming out. In that incident on the M6 Motorway, armed police escorted passengers off the bus but later determined the incident to be a false alarm unconnected to the arrests.
"Importantly, we are not treating this as a counter-terrorism incident," a police statement said.
In the terror probe investigation, five men and one woman, ages 21 to 29, were arrested in several locations across London by officers from Scotland Yard's Counter Terrorism Command.
The arrests were the "executive action" phase of a long-running investigation led by British intelligence service MI-5.
The men and woman were all arrested on suspicion of the commission, preparation or instigation of acts of terrorism under the Terrorism Act 2000, police said.
The suspects were taken to a southeast London police station where they are in custody.
Authorities would not disclose further details of the case that might compromise their strategy for interviewing the suspects.
What they seized in the searches is unknown.
Police said the arrests in London are related to a possible plot involving Islamist extremists and potential targets in the United Kingdom.
The incident and arrests occurred days after two people were picked up on suspicion of plotting an attack on the London Olympic canoeing venue.
The U.K.'s Ministry of Defense has confirmed that they are providing assistance to police at the incident in the M6.
ABC News' Jeffrey Kofman contributed to this report.