Crews prepare for demolition at Francis Scott Key bridge collapse site

After weeks of preparation, crews are scheduled to conduct a controlled demolition Sunday to break down the largest remaining span of the collapsed Francis Scott Key Bridge in Maryland, which came crashing down under the impact of a massive container ship on March 26.

Of the crew members, 20 are from India and one is Sri Lankan.

The steel span landed on the ship's bow after the Dali lost power and crashed into one of the bridge's support columns shortly after leaving Baltimore. Since then, the ship has been stuck among the wreckage and Baltimore's busy port has been closed to most maritime traffic.

Six members of a roadwork crew plunged to their deaths in the collapse. The last of their bodies was recovered from the underwater wreckage earlier this week. All the victims were Latino immigrants who came to the U.S. for job opportunities. They were filling potholes on an overnight shift when the bridge was destroyed.

The controlled demolition will allow the Dali to be refloated and guided back into the Port of Baltimore. Once the ship is removed, maritime traffic can begin returning to normal, which will provide relief for thousands of longshoremen, truckers and small business owners who have seen their jobs impacted by the closure.

The Dali's 21-member crew will shelter in place aboard the ship while the explosives are detonated.

William Marks, a spokesperson for the crew, said they would shelter in a designated safe place during the demolition. All precautions are being taken to ensure everyone's safety, he said in an email.

In a videographic released this week, authorities said engineers are using precision cuts to control how the trusses break down. They said the method allows for surgical precision and is one of the safest and most efficient ways to remove steel under a high level of tension. The steel structure will be thrust away from the Dali when the explosives send it tumbling into the water, according to the videographic.

Once it's demolished, hydraulic grabbers will lift the resulting sections of steel onto barges.

It's important to note that this controlled demolition is not like what you would see in a movie, the video says, noting that from a distance it will sound like fireworks or loud thunder and give off puffs of smoke.

Officials previously said they hoped to remove the Dali by May 10 and reopen the port's 50-foot (15.2-meter) main channel by the end of May.

The Dali crew members haven't been allowed to leave the grounded vessel since the disaster. Officials said they have been busy maintaining the ship and assisting investigators.

The National Transportation Safety Board and the FBI are conducting investigations into the bridge collapse.

Danish shipping giant Maersk chartered the Dali for a planned trip from Baltimore to Sri Lanka, but the ship didn't get far. Its crew sent a mayday call saying they had lost power and had no control of the steering system. Minutes later, the ship rammed into the bridge.

Officials have said the safety board investigation will focus on the ship's electrical system.