A mayday warning from the ship that slammed into a Baltimore bridge saved lives by prompting officials to stop cars from crossing, Maryland Governor Wes Moore said.

“We’re thankful between the mayday and collapse we had officials that were able to begin stopping the flow of traffic,” Moore told reporters Tuesday.“Many of the vehicles were stopped before they got onto the bridge, which saved lives in a very, very heroic way.”

Moore said he didn’t yet have information about whether any vehicles were on the Francis Scott Key Bridge when the Dali, a 32,000-ton ship carrying about 4,900 containers, collided with it around 1:30 a.m. Eight construction workers were on the span, six of whom remain missing. One has been hospitalized and another has been in contact with authorities but isn’t in the hospital. 

The Singapore-flagged vessel reported a power issue before hitting the bridge at about eight knots, a “rapid speed,” Moore said. Given the immediate focus on search-and-rescue operations, there’s no timeline for when shipping will resume, he said. Baltimore’s port is one of the busiest on the US East Coast and the nation’s largest for handling cars and light trucks.

The Dali experienced a momentary loss of propulsion, said the Maritime and Port Authority of Singapore, citing the vessel’s manager and operator, Synergy Marine. As a result, the ship was unable to maintain its desired heading. 

“The vessel was reported to have dropped its anchors as part of the vessel’s emergency procedures prior to its impact with the bridge,” the Singapore port authority said. “The vessel was under pilotage at the time of the incident.”