The White House, Pentagon and US Capitol building were all evacuated as a strong earthquake rocked America’s East Coast.
The epicentre was at Mineral, Virginia, about 90 miles south-west of Washington DC, but the seismic waves were felt as far north as Boston and as far south as Charlotte in North Carolina.
There were no reports of serious injuries in the 5.8 magnitude quake – but buildings were damaged, including Washington’s National Cathedral, where three spires of the central tower broke off.
In the US capital, thousands of federal workers were told to leave their offices as government buildings were shut down. Items fell to the floor from shop shelves.
The Capitol building on the Mall was closed and tourists asked to leave the Monuments.
The floor of the US Senate shook before staff headed to the exits. Some minor damage could be seen in the rotunda, under the dome of the Capitol.
The US Congress is in recess so most politicians were away.
“I thought at first somebody was shaking my chair and then I thought maybe it was a bomb,” said Senate aide Wendy Oscarson-Kirchner.
As workers were sent home, streets in and around the capital soon became gridlocked with the exodus of traffic.
It was the largest quake in Virginia since 1897 and struck at a shallow depth, increasing its potency.
In New York, the tremors led to courthouses and the City Hall to be evacuated and work was halted at the World Trade Centre construction site.
Control towers at John F. Kennedy International Airport in New York City and Newark Liberty Airport in New Jersey were also evacuated.
And flights were grounded briefly in Washington, Philadelphia and New York.
President Obama was on holiday at Martha’s Vineyard in Massachusetts at the time. He held a conference call shortly afterwards with senior advisors.
Rachel Racusen, of the Federal Emergency Management Agency, said: “Though there are no early reports of major damage or requests for assistance at this time, preliminary damage assessments are currently taking place in all affected states and we will continue to work closely with their emergency management officials.”
It is one of the largest quakes to hit the East Coast in years.
The area is bracing itself for the arrival of Hurricane Irene, which is hurtling through the Bahamas and is expected to hit mainland America at the weekend.
