Man Throws Smoke Bomb at Diners and Escapes Through Subway Hatch An unidentified man was caught on video emerging from New York subway hatch.

 -- Police in New York were searching today for a man who popped up from a sidewalk subway hatch and lobbed a smoke bomb at a pair of fancy restaurants, sending diners scrambling.

The man was captured on video emerging from a hatch used for emergency exits from the New York subway system. The hatches are used by emergency responders to evacuate riders from the subway if necessary.

On security video, diners were seen fleeing their tables as smoke started to overtake the outdoor eating areas for the Da Silvano restaurant and the Bar Pitti restaurant. According to the New York Police Department, no one was injured.

One of those at the restaurant was actress Rose McGowan, who tweeted about her expierence shortly after the smoke cleared.

Police said they were looking for a white male approximately 20 years old with blond wavy hair.

While diners were unharmed, at least one expert said law enforcement should be concerned that the man was able to both exit and enter the emergency subway gate without being captured.

Former FBI agent Brad Garrett said the event could be a good learning experience for authorities to understand how emergency services might respond in a similar attack.

"It's clearly a wake-up call," said Garrett, an ABC News contributor. "When you get into a city of the size of New York or even just the one borough of Manhattan, you literally cannot cover every single avenue. You do the best you can and try to learn from every situation and figure out where you have a vulnerability."

He pointed out that New York City has hundreds of miles of subway tunnels.

"The first thing the NYPD and the subway transit police are going to have to look at is the vulnerability of the subway tunnel system," he said. "How did this guy get into the system? How he did he move for I'm going to say a number of minutes undetected and then exit the subway system?

The New York Police Department Public Information Office told ABC News they had no updates on the case or whether added security will be used to protect subway emergency exits.

Staff at both Bar Pitti and Da Silvanos declined to discuss the incident.