BALTIMORE, Mar. 27 (Reuters) - Six workers were missing and presumed dead from a bridge that collapsed in Baltimore Harbor early on Tuesday when a massive cargo ship crippled by a power loss rammed into the structure, forcing closure of one of the busiest ports on the U.S. Eastern Seaboard.

U.S. Coast Guard and Maryland State Police officials said that based on the frigid temperature of the water and the length of time that had elapsed since the bridge came down there was little if any chance that the six missing could be found alive.

The Singapore-flagged container vessel named Dali, heading out of the harbor bound for Sri Lanka, plowed into a support pylon of the Francis Scott Key Bridge over the mouth of the Patapsco River at about 1:30 a.m. (0530 GMT).

A trestled section of the of the 1.6-mile (2.57 km) span almost immediately crumpled into the icy water, sending vehicles and people into the river.

Rescuers pulled two survivors to safety, one of whom was hospitalized. But active search-and-rescue operations were suspended about 18 hours after the tragedy, authorities said.

The eight individuals were part of a work crew filling potholes on the road surface of the bridge when the accident occurred, officials said earlier.

The ship reported a power failure before impact, which enabled officials to stop traffic on the bridge before the collapse.

"By being able to stop cars from coming over the bridge, these people are heroes. They saved lives last night," Maryland Governor Wes Moore said at a news briefing hours later. The bridge was up to code and there were no known structural issues, Moore said.

Photo from Reuters