Researchers released 3-D sonar maps and images of the steamship SS City of Rio de Janeiro that was lost in the waters off San Francisco over a century ago.

The shipwreck struck jagged rocks in 1901 and went down, killing 128 of the 210 people aboard; many consider this to be the worst maritime disaster in San Francisco history, the National Oceanic and Atmospheric Administration (NOAA) reported. Fishermen in the area were able to rescue 82 survivors when they heard the ship's distress call.

"We are undertaking this exploration of the San Francisco Bay in part to learn more about its maritime heritage as well as to test recent advances in technology that will allow us to better protect and understand the rich stories found beneath the Bay's waters," said James Delgado, director of maritime heritage for NOAA's Office of National Marine Sanctuaries.

The wreck was first discovered in the 1980s, but its exact location remained unknown until recently. In November, Hibbard Inshore and Bay Marine Services donated a research vessel and crew, along with a high-powered remotely operated vehicle that allowed researchers to excavate the historic shipwreck.

During this expedition the team precisely located the wreckage in 287 feet of water and partially buried in the mud. They created the first detailed sonar and three-dimensional images of City of Rio.

"The level of detail and clarity from the sonar survey is amazing," said Robert Schwemmer, West Coast Regional Maritime Heritage Coordinator. "We now have a much better sense of both wrecks, and of how they not only sank, but what has happened to them since their loss."

In the past the ship (which carried passengers and freight to and from San Francisco, Honolulu, Yokohama, Japan and Hong Kong ) was rumored to have held Chinese silver treasure, but it is believed these were actually just bars of tin.

"Today the wreck is broken and filled with mud, and it is a sealed grave in fast, dangerous waters in the main shipping lanes," Delgado said.