METRO police officer John Sheiffield observes passengers and what they're carrying at a METRO subway platform.
WASHINGTON (CNN) -- Terrorism concerns surrounding the one-year anniversary of the death of al Qaeda leader Osama bin Laden prompted authorities to elevate visible security Wednesday on Washington's Metrorail system.
"There is no specific or credible threat. We are mindful that, in the past, al Qaeda has shown an interest in anniversaries and significant dates," said Philip Stewart, a Washington Metropolitan Transit Authority spokesperson.
Officers with the Metro Transit Police Department's anti-terror team fanned out in the subway system Wednesday with bomb-sniffing dogs and extra officers, according to Deputy Chief Mark Olson.
"On days such as today, where it is an anniversary, we tend to deploy our forces a little bit differently to provide a little more visibility," said Olson. Officials plan to continue the heightened security throughout the week.
The transit police are also working with federal agencies and local law enforcement, said Olson. "Law enforcement agencies from Boston to Washington are engaging in transit-related activities such as high visibility deployment to increase awareness," said Olson.
The coordinated effort is part of a public awareness campaign, Rail Safety Week.
Olson said anti-terror officers did not discover anything suspicious during patrols on Wednesday.