CAPE CANAVERAL, Fla., Jan. 28, 1986 (UPI) -- Military ships and aircraft ranged almost 175 miles across the Atlantic Ocean east of Florida's spaceport Tuesday in a futile search for survivors of the shuttle Challenger disaster, and warned private vessels to stay away for fear toxic debris.
All the searchers reported finding by dusk, when air operations were halted for the night, was bits and pieces of the $1.1 billion space freighter. There was no sign of the seven crewmembers, five men and two women including New Hampshire high school teacher Christa McAuliffe.
Search spokesman Air Force Col. John Shults said the sea bottom probably would be combed eventually for parts of the shuttle that did not float.
''The first thing we wanted to do was pick up survivors,'' Shults said about seven hours after Challenger exploded 10 miles above Earth and plunged into the Atlantic.
''That's now probably out of the question. Now we want to pick up the debris. Some of it may be covered with toxic chemicals, so we're warning civilians not to pick anything up.''
Rescue teams searched a rectangle 58 miles wide and 115 miles long extending almost due East from a point 50 miles off the Florida spaceport coast.
''We're told the area is a relatively shallow area on a shelf approximately 75 to 150 feet deep, 200 feet max,'' said Air Force Lt. Col. Robert Nicholson, another spokesman for the search team.
Planes ranged over the ocean marking debris for later pickup by ships.
Shults said the largest piece of debris he knew had been found was 5 to 10 feet long and about 2 feet wide.
Nicholson said the search force included seven ships, five fixed-wing aircraft and eight helicopters. The aircraft quit their search just before dusk, with plans to resume at dawn Wednesday, but the ships kept their vigil throughout the night.
He said debris rained into the ocean for ''nearly an hour'' after Challenger burst into a fireball, slowing rescue teams from entering the area. As for details of what had been found, he said it was too early to be certain.
The space shuttle was designed so a crew could survive an emergency landing in water and to keep an intact shuttle afloat, as long as it can glide to the surface of the ocean under full control.
''If it's a chopper or an airplane that spots it, they're doing the coordinates for later pickup,'' Nicholson said. ''Dredging, that sort of thing, isn't a priority right now. Rescue is the priority and collection of debris on the surface.''
A C-130 Coast Guard airplane and two Air Force H-3 helicopters led the recovery effort from the air. In addition, one NASA solid-fuel rocket recovery ship and a Coast Guard hydrofoil already were routinely on station to keep ships from straying into the area where the shuttle's solid-fuel rockets fall by parachute after being jettisoned from the ship.
Other ships and helicopters were sent to the scene later.
''There was a Coast Guard hydrofoil that was involved in clearing the impact zone, standing just outside the impact zone that had to remain staying there until after the Cape range safety people cleared him into the area because of the debris,'' Nicholson said. ''Everybody started to move toward the area immediately afterwards. They had to remain outside for nearly an hour.''
Like all American space vehicles, shuttles are wired with explosive devices so they can be destroyed by ground command if a catastrophic failure sends them veering out of control over populated areas.
Nicholson said local scallop crews volunteered to help in the search effort and offered to use their nets for dredging, but such activities could not be carried out until officials were sure the self-destruct devices have been found.
