Officials at the Washington area airports are urging travelers to remain vigilant in the wake of the Brussels attacks.

“Passengers can assist by remaining vigilant and remembering: ‘If you see something, say something,'”  Christopher Paolino, a spokesman for the Metropolitan Washington Airports Authority said.

“Passengers who see something suspicious should pass that information to Airport Police or an airport employee,” Paolino said in a statement. “We all have a responsibility in helping to keep our airports safe.”

Officials in the Washington region have said there is “no indication of a specific threat” to the region’s transportation infrastructure following explosions Tuesday at the Brussels airport and a train station.

MWAA officials say the airports have “a robust security structure” in place.

Earlier Tuesday, the Metro Transit Police said it was adding additional K9 sweeps and patrols as a precaution.

Updated at 9:24 a.m.

Officials at Baltimore Washington International Airport said Tuesday they are “working closely” with federal and state law enforcement agencies after the Brussels attacks. There is “no indication of a specific threat” at the facility, officials said in a statement.

Authorities at the airport said the facility “consistently operates with a high level of security and vigilance.”

They would not detail exactly what measures they are taking. The statement said “there are measures in place that travelers would recognize, and others that may not be easily observed.”

Other agencies said they were on alert as well and reminding people to stay alert.

Updated at 8:07 a.m.

Metro said it will have “additional K9 sweeps” and patrols Tuesday morning as a precaution following the Brussels attacks. And Alexandria police said they are also patrolling Metro lots Tuesday morning.

Officials said in a tweet that they had “no known, specific or credible threat” to the Metro system “at this time.”

The transit agency said it is also closely monitoring the situation in Brussels with its federal partners, according to a tweet.

Officials with Metro reminded riders to report any suspicious activity.