A Baltimore bridge has crashed into the Patapsco River after being struck by a large boat this morning.
Footage from Maryland showed the 9,000-foot structure crumbling after the vessel collided with one of its pillars.
Baltimore Mayor Brandon Scott revealed emergency services were on scene following the incident.
He said: "Emergency personnel are on scene, and efforts are underway."
Baltimore bridge crashes into river after being struck by large boatGB NEWS
Flight tracking website FlightRadar24 showed the Maryland State Police circling the 47-year-old bridge in a helicopter.
Baltimore City Fire's PIO later confirmed at least seven people were believed to be in the Patapsco River.
Chief Kevin Cartwright said "as many as seven individuals and several vehicles" have fallen into the river.
An update indicated 20 construction workers and three civilian cars were believed to have been on the bridge unaccounted for.
The structure is estimated to carry around 12 million vehicles every year.
An image of the ship colliding with the structure (left)
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The Old Line State's Governor Wes Moore issued a statement confirming a state of emergency in Maryland.
He said: "My office is in close communication with US Transportation Secretary Pete Buttigieg, Baltimore Mayor Brandon Scott, Baltimore County Executive Johnny Olszewski, and the Baltimore Fire Department as emergency personnel are on the scene following the collapse of the Francis Scott Key Bridge.
"I have declared a State of Emergency here in Maryland and we are working with an interagency team to quickly deploy federal resources from the Biden Administration.
"We are thankful for the brave men and women who are carrying out efforts to rescue those involved and pray for everyone’s safety.
"We will remain in close contact with federal, state, and local entities that are carrying out rescue efforts as we continue to assess and respond to this tragedy."
Buttigieg also said: "’I've spoken with Gov. Moore and Mayor Scott to offer USDOT’s support following the vessel strike and collapse of the Francis Scott Key bridge. Rescue efforts remain underway and drivers in the Baltimore area should follow local responder guidance on detours and response."
Footage from the scene circulated on social media before any official statements were made
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Confirming the incident, Fire Boat operator Andrew Doyle said: "A container ship has struck the Key Bridge in Baltimore.
"Part of the bridge has collapsed. Multiple fire and police boats are on the way."
Maryland's Transportation Authority separately announced: "All lanes closed both directions for incident on I-695 Key Bridge. Traffic is being detoured."
Footage from the scene circulated on social media before any official statements were made.
The ship was reportedly a Singaporean-flagged container called Dali.
Coast Guard vessels surrounded the ship at around 3am local time (7am GMT).
Users expressed their shock with the situation, with one writing: "This is devastating."
Other people described the incident as "wildly catastrophic" and like a "nightmare".