|Relics found from the Franklin Expedition. Illustrated London News 1854|
Searches continued and over the decades various clues turned up including notes left in a cairn on 11 June 1847 saying that Erebus and Terror had been trapped in pack ice for over a year; the men finally abandoned the ships on 22 April 1847. Twenty-four officers and crew had died by this time, including Captain Franklin.
In 1981 an examination of crew remains from Beechey Island revealed that they probably died of pneumonia and/or tuberculosis. Other bodies found on King William Island showed cut marks on bones consistent with cannibalism. The entire expedition probably perished as a combined result of exposure, starvation, and disease. But poisoning may have hastened their deaths.
The poison? Lead from the tins of food with which the ships had been provisioned. High levels of lead were also found when analyzing the bodies. This theory is bolstered by a recent analysis of a soup can left by a rescue crew in 1854. The lead levels in the can were "off the charts". (Discover Magazine quoting The Times Colonist).
Lead poisoning can cause cramps, joint pain, severe anemia, mental confusion, memory loss, kidney dysfunction, and death. If the lost crew were subsisting primarily on their tinned provisions, and if most or all of the cans had the same extremely high levels of lead found in the analyzed can (which is highly likely), then it's entirely possible that lead poisoning alone may have doomed a portion of the crew.
*The well-preserved wreck of HMS Erebus was finally found in 2014, in about 40 feet of water near King William Island, about 1,200 miles northwest of Toronto.