"Boston Bombing" - Authorities search for 'dark-skinned or black male' as police guard another potential suspect in Boston hospital.

Boston marathon suspect surrounded by police.

"Boston Bombing" - Authorities search for 'dark-skinned or black male' as police guard another potential suspect in Boston hospital.(DM). Police are seeking a suspect in the Boston bombings who is described as a 'dark-skinned or black male' carrying a backpack, while authorities are also reportedly questioning a potential suspect at an area hospital, according to reports. The suspect at large was spotted at the scene of the twin explosions at the Boston Marathon finish line on Monday and he wearing a black sweatshirt with a hood, according to authorities. Five minutes before the first explosion, officials said the person attempted to gain entry to a restricted area and was turned away. Authorities say he may be a foreign national, based on his accent.

Another potential suspect was also being questioned by police at an area hospital Monday afternoon. Several news outlets reported that he is a 20-year-old Saudi national in the country on a student visa.

The person was among dozens injured - at least two fatally - by the blasts.

A civilian at the scene of the blasts claimed the potential suspect was acting suspiciously. The civilian reportedly chased him down and tackled him after the explosions.

The man is said to be cooperating with investigators and denies any involvement. Police have not revealed where he is being treated, but several witnesses saw AFT agents with automatic weapons entering Brigham and Women's Hospital several hours after the blasts.

Texas Rep. Michael McCaul, chairman of the House Homeland Security Committee, told CNN that he been briefed in an intelligence meeting about the development.

Authorities were still denying around 8 p.m. Monday that they have any definitive suspects in custody. They said they were questioning several people Monday but had not yet labeled anyone a suspect. Pictures of a man in handcuffs surrounded by law enforcement officials circulated Twitter Monday, but authorities didn't identify the man or say whether his arrest was related to the blasts.

'At this time, we haven't been notified of any arrests or anyone apprehended,' a police spokesperson said. Other reports suggested one line of inquiry was an individual caught on camera before the attack carrying multiple backpacks into the area 20 minutes before the deadly blasts.

Police departments across the country including San Francisco and New York have been put on heightened alert. In London security will now be assessed ahead of the marathon being held there on Sunday. A no-fly zone was temporarily introduced over the city and has now been lifted. Read the full story here.

Related: Hmmm.......the following story and headline have now 'Disappeared'.