WASHINGTON (Reuters)—A strong earthquake struck the U.S. East Coast and was felt as far away as Canada on Tuesday, shaking buildings in many cities, delaying flights and trains and sending thousands of frightened workers into the streets.

There were no reports of major damage or injuries from the 5.9 magnitude quake, which the U.S. Geological Survey said was centered in Mineral, Virginia, at a very shallow depth of 0.6 miles.

The Pentagon and the U.S. Capitol were briefly evacuated in Washington, and thousands of panicked office workers scurried into the streets up and down the East Coast as the lunchtime quake sent items crashing to the floor from store and office shelves.

"We were rocking," said Larry Beach, who works at the U.S Agency for International Development in downtown Washington, 83 miles from the quake's epicenter. "It was definitely significant."

Earthquakes of magnitude 5.5 to 6.0 can cause damage to buildings and other structures, especially if shallow. The U.S. East Coast does not normally feel quakes of this strength.

Amtrak reduced speed between Washington and Baltimore, track crews inspected East Coast stations and rails for damage and warned passengers to expect delays.

Two nuclear reactors at a power plant in Virginia went off line, while traffic lights were knocked out throughout Washington.

Three pinnacles in the central tower of the Washington National Cathedral, the highest building in the city, broke off in the quake, a spokesman said.

Chandeliers swayed in the U.S. Capitol and the floor of the U.S. Senate shook before staff headed for the doors. The U.S. Congress is in recess.

"I thought at first somebody was shaking my chair and then I thought maybe it was a bomb," said Senate aide Wendy Oscarson-Kirchner.

Phone service was disrupted throughout the region as network congestion prevented cell phone users from making calls. A Verizon Wireless spokesman said there were no reports of damage to its network but congestion disrupted service for about 20 minutes after the quake.

NEW YORK PANIC

In New York, the tremors prompted evacuations of courthouses, City Hall and halted work at the World Trade Center 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 while authorities inspected control towers and runways.

Fire department and police officials in Dutchess County, north of New York City, reported structural damage to some buildings.

"We're getting a lot of calls on buildings shaking but there's no report of any structural damage at this time. Just panicked people calling about buildings shaking," a spokesman for the New York City Fire Department said.

Buildings in Boston were evacuated, while the quake was felt as far away as Toronto.

Some people who experienced the swaying at their offices in Boston said they felt their stomachs turn.

The quake was the largest in Virginia since 1897.