(Updates with latest developments)

By Lisa Shumaker

March 27 (Reuters) - Baltimore's Francis Scott Key

Bridge collapsed on Tuesday after a container ship smashed into

a pylon, with the six people missing presumed dead after falling

into the frigid water below. Authorities stopped people from

using the bridge after the ship sent out a mayday call, saving

lives.

It may be some time before one of the busiest ports on the U.S.

Eastern Seaboard can reopen, but experts say the collapse is

unlikely to trigger a supply chain crisis.

WHAT HAPPENED IN BALTIMORE?

Shortly after 1 a.m. ET (0500 GMT), a container ship named

the Dali was sailing down the Patapsco River on its way to Sri

Lanka. At 1:24 a.m., it suffered a total power failure and all

its lights went out.

Three minutes later, at 1:27 a.m., the container ship struck

a pylon of the bridge, crumpling almost the entire structure

into the water.

The bridge was up to code and there were no known structural

issues, Maryland Governor Wes Moore said.

Tuesday's disaster may be the worst U.S. bridge collapse

since 2007, when a design error caused the I-35W bridge in

Minneapolis to plunge into the Mississippi River, killing 13

people.

ARE THERE ANY CASUALTIES?

Six people are missing, and rescuers have lost hope of

finding survivors. The six presumed dead include workers from

Mexico, Guatemala and El Salvador, according to the Mexican

Consulate in Washington.

Efforts have switched to looking for bodies in the

50-foot-deep waters surrounding the twisted ruins.

At the time of the crash, a construction crew was fixing

potholes on the bridge and eight people fell 185 feet (56

meters) into the river where water temperatures were 47 F (8

C). Two workers were rescued, one unharmed and one injured.

According to research for the Federal Aviation

Administration, that is the upper limit of what a human could

survive falling into water.

Authorities saved lives by stopping vehicles from using the

bridge after the ship sent out a mayday call, the Maryland

governor said.

The ship also dropped its anchors to slow the vessel, giving

transportation authorities time to clear the bridge.

WHY DID THE BRIDGE COLLAPSE?

The metal truss-style bridge has a suspended deck, a design

that contributed to its collapse, engineers say. The ship

appeared to hit a main concrete pier, which rests on soil

underwater and is part of the foundation.

WHO WILL PAY FOR THE DAMAGE?

President Joe Biden promised to visit Baltimore soon and said he

wanted the federal government to pay to rebuild the bridge.

The Transportation Department can award "quick release"

emergency relief funds that are typically a few million dollars.

To replace the bridge, Congress would need to approve funding.

After the bridge collapse in 2007 in Minnesota, Congress

allocated $250 million.

WHAT DO WE KNOW ABOUT THE SHIP THAT WAS INVOLVED?

The Dali was leaving Baltimore en route to Colombo, Sri

Lanka.

None of the 22 crew members were hurt, the ship's manager,

Synergy Marine Group said.

The registered owner of the Singapore-flagged ship is Grace

Ocean Pte Ltd, LSEG data show. The ship measures 948 feet (289

meters) - as long as three football fields placed end to end. It

was stacked high with containers but was capable of carrying

twice as much cargo. Safety investigators recovered the ship's

black box, which can tell them the vessel's position, speed,

heading, radar, bridge audio, and radio communications as well

as alarms.

The same ship was involved in an incident in the port of

Antwerp, Belgium, in 2016, when it hit a quay as it tried to

exit the North Sea container terminal.

A later inspection in June 2023 carried out in San Antonio,

Chile, found the vessel had "propulsion and auxiliary machinery"

deficiencies, according to data on the public Equasis website,

which provides information on ships.

WHAT DO WE KNOW ABOUT THE BRIDGE THAT COLLAPSED?

The Francis Scott Key Bridge was one of three ways to cross the

Baltimore Harbor and handled 31,000 cars per day or 11.3 million

vehicles a year.

The steel structure is four lanes wide and sits 185 feet (56

meters) above the river.

It opened in 1977 and crosses the Patapsco River, where U.S.

national anthem author Francis Scott Key wrote the "Star

Spangled Banner" in 1814 after witnessing the British defeat at

the Battle of Baltimore and the British bombing of Fort McHenry.

HOW WILL THE BRIDGE COLLAPSE IMPACT THE BALTIMORE PORT?

Traffic was suspended at the port after the accident. It is one

of the smallest container ports on the Northeastern seaboard,

handling about a tenth of the volume that passes through the

Port of New York and New Jersey.

The flow of containers to Baltimore can likely be

redistributed to bigger ports, said container shipping expert

Lars Jensen. However, there could be major disruptions in

shipping cars, coal and sugar.

It is the busiest U.S. port for car shipments, handling at

least 750,000 vehicles in 2023, according to data from the

Maryland Port Administration.

In 2023, the port was the second busiest for coal exports.

It is also the largest U.S. port by volume for handling farm

and construction machinery, as well as agricultural products

such as sugar and salt.

(Writing by Lisa Shumaker; Editing by Daniel Wallis and Stephen

Coates)