BALTIMORE (AP) — Crews are expected to conduct a controlled demolition Monday evening to break down the largest remaining steel span of the collapsed Francis Scott Key Bridge in Baltimore, a major step in the cleanup as officials seek to fully reopen the port’s busy shipping channel by the end of the month.

Engineers have been preparing for weeks to use explosives to break down the span, which is an estimated 500 feet (152 meters) long and weighs up to 600 tons (544 metric tons). It landed on the ship’s bow after the Dali lost power and crashed into one of the bridge’s support columns shortly after leaving the Port of Baltimore. Since then, the ship has been stuck amidst the wreckage and the port has been closed to most maritime traffic.

The demolition was postponed Sunday because of thunderstorms.

“This is a best practice,” Gov. Wes Moore said at a news conference Monday. “Safety in this operation is our top priority.”

Moore noted that there have been no injuries during the cleanup and that the controlled demolition will allow crews to maintain a strong safety record.

Six construction workers were killed in the collapse.

READ MORE Controlled demolition at Baltimore bridge collapse site postponed due to weather Body of last missing construction worker recovered from Baltimore bridge collapse site Maryland officials release timeline, cost estimate, for rebuilding bridge

Engineers are using precision cuts to control how the trusses break down, causing them to fall away from the Dali when explosives send them tumbling into the water, officials said. Once it’s demolished, hydraulic grabbers will lift the broken sections of steel onto barges.

The demolition will allow the Dali to be refloated and guided back into the port. 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 whose jobs have been affected by the closure.

The Dali’s 21-member crew will remain below deck on the ship while the explosives are detonated. U.S. Coast Guard Rear Admiral Shannon Gilreath said containers on the ship’s decks will further separate the crew from the action.

Fire teams will be stationed in the area in case they’re needed, and a “water curtain” will help shield the ship and its cargo from potential flames. Gilreath said a fire is not expected, but if one happens, the ship’s crew will be best placed to help extinguish it.

“We’ve taken into account the safety of those crew members from the very beginning,” he said. “They’re staying onboard because they’re part of the ship. They are necessary to keep the ship safe and operational.”

Crew members haven’t left the ship since the March 26 collapse, which occurred shortly after the ship set out for Sri Lanka. Officials have said they’ve been busy maintaining the grounded ship and assisting investigators. Twenty of the crew members are from India and one is Sri Lankan.

State and federal officials have commended the salvage crews and other members of the cleanup operation who helped recover the remains of the six construction workers who were killed in the collapse.

The last body was recovered from the underwater wreckage last week. All of 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.

Officials said the operation remains on track to reopen the port’s 50-foot (15-meter) deep draft channel by the end of May. Until then, crews have established a temporary channel that’s slightly shallower. Officials said 365 commercial vessels have passed through the port in recent weeks. The port normally processes more cars and farm equipment than any other in the country.

Former House Speaker Nancy Pelosi, a Baltimore native whose father and brother served as mayor decades ago, compared the Key Bridge disaster to the overnight bombardment of Baltimore’s Fort McHenry, which long ago inspired Francis Scott Key to write the Star-Spangled Banner during the War of 1812. She said both are a testament to Maryland’s resilience.

Pelosi, a Democrat who represents California’s 11th district, attended Monday’s news conference with two of her relatives. She praised the collective response to the tragedy as various government agencies have come together, working quickly without sacrificing safety.

“Proof through the night that our flag was still there,” she said. “That’s Baltimore strong.”