Six workers are missing and presumed dead following the collapse of the Francis Scott Key Bridge in the United States city of Baltimore, as authorities called a halt to search-and-rescue efforts.

US Coastguard and Maryland State Police officials said late on Tuesday that search-and-rescue operations had been suspended as dive teams were facing increasingly dangerous conditions in the darkened waters of the Patapsco River.

“At this point, we do not believe we are going to find any of these individuals still alive,” Coastguard Rear Admiral Shannon Gilreath said at a news conference.

State Police Colonel Roland Butler said authorities intended to return divers to the water after sunrise on Wednesday in an effort to recover the deceased’s remains.