Six people are missing and presumed dead after a container ship hit the landmark Francis Scott Key Bridge in the US city of Baltimore.

The Coast Guard said it had suspended its search and begun a recovery effort.

Several vehicles were crossing the bridge, which is more than 2.6km (1.6 miles) long, when it collapsed after the vessel hit a support.

Officials say the ship suffered a "power issue" and issued a distress call moments before the crash.

Boats and helicopters were part of a huge search and rescue effort searching for the six missing people. Two others were pulled from the water, with one in a serious condition.

Rear Admiral Shannon Gilreath of the US Coast Guard said in the evening that the remaining missing men were presumed dead based on the temperature of the waters they had fallen in and the length of time they have been under water.

Authorities say they were part of a construction crew repairing potholes at the time the bridge snapped.

The Singapore-flagged container ship, Dali, struck a support column on the 47-year-old bridge at 01:30 (05:30 GMT), causing it to collapse.

It had departed from the terminal at Port Breeze at around 00:45 bound for the Sri Lankan capital, Colombo.

A US federal government agency said the vessel "lost propulsion" as it was leaving the port.

The crew then warned Maryland transport officials of a possible collision, according to an unclassified Cybersecurity and Infrastructure Security Agency report on the incident.

Maryland state governor Wes Moore said he could confirm that "the crew notified authorities of a power issue", adding that the ship had lost power before smashing into one of the columns supporting the bridge.

A number of vehicles, including "one the size of a tractor-trailer", plunged into the water below, officials said.

Baltimore fire department, the US Coastguard and other agencies from the state of Maryland have been involved in the rescue operation.

Baltimore Fire Chief James Wallace confirmed that two people had been rescued and one of them had been "transported to a local trauma centre... in a very serious condition".

Mr Wallace said the tide was posing a challenge to rescue efforts. Local officials said another huge concern for rescue teams was the freezing conditions, with air temperatures of about 3C (37.4F) near the bridge.

Baltimore Mayor Brandon Scott described the incident as an "unthinkable tragedy", adding the focus right now should be on "the people, the lives, the souls… there are people in the water that we have to get out and that's the only thing we should be talking about."

Maryland Transportation Secretary Paul Wiedefeld said engineers were at the site determining the structural impact of the collapse.

Shipping company Synergy Marine Group told the BBC there were 22 people on the ship, including an all-Indian crew and two Baltimore locals serving as port pilots, and that there were no reports of any injuries.

Pilots are people with local knowledge who board ships and help manoeuvre them into and out of a port.

The company said in a statement that the exact cause of the incident had yet to be determined and that it was "fully co-operating" with federal agencies.

Shipping giant Maersk said it had chartered the vessel and was carrying its customers' cargo.

"We are horrified by what has happened in Baltimore, and our thoughts are with all of those affected," it said in a statement. No Maersk crew and personnel were onboard the vessel.

US President Joe Biden said he would travel to Baltimore as soon as possible, and that search and rescue efforts should be prioritised.

"I've directed my team to move heaven and earth to reopen the port and rebuild the bridge as soon as humanly possible," he said.

He said the collapse had been an accident and that federal government would "pay for the entire cost of that bridge" - the spending, he added, would need to be approved by members of congress. (BBC)

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