epa02552726 A NASA handout dated 28 January 1986 shows the Space Shuttle Challenger accident after its launch from the Kennedy Space Center in Cape Canaveral, in Florida, USA.
28 January 2011 will mark the 25th anniversary of the Space Shuttle Challenger disaster in which 7 crew members including US teacher Christa McAuliffe died. EPA/NASA / HANDOUT 
By Dan Whitcomb
The divers contacted NASA after spotting a large, clearly modern object mostly covered in sand at the bottom of the ocean and bearing the shuttle's distinctive tiles, the space agency said in a written statement.
"This discovery gives us an opportunity to pause once again, to uplift the legacies of the seven pioneers we lost, and to reflect on how this tragedy changed us," NASA administrator Bill Nelson said in the statement.
The divers were exploring the sea floor off Florida earlier this year as part of a History Channel documentary called "The Bermuda Triangle: Into Cursed Waters" about the swath of the Atlantic Ocean long subject to myths surrounding the supposed supernatural vanishing of planes and ships.
They were looking for the wreckage of a PBM Martin Mariner Rescue Plane that disappeared without a trace on Dec. 5, 1945, while searching for five U.S. Navy torpedo bombers that had also went missing that day.
The find marks the first time in 25 years that a piece of the Challenger has been located.
Nelson said NASA was trying to determine whether to recover the wreckage and "what additional actions it may take regarding the artifact that will properly honor the legacy of Challenger's fallen astronauts and the families who loved them."
The Challenger erupted into a ball of flame 73 seconds after lifting off from Kennedy Space Center on Jan. 28, 1986. All seven crew members were killed, including school teacher Christa McAuliffe.
Subsequent investigations blamed the disaster on compromised O-Ring seals on a solid rocket booster, worsened by unusually cold temperatures.
It remains one of the worst disasters in the history of the U.S. space program.