The key, described by police as "not machine made" and likely to have been roughly copied by the inmates during the intricate planning of the escape, was found by one of Parkhurst's clerical staff.
The abandoned key was put through a series of forensic tests yesterday. An immediate check found it did open important doors inside the Isle of Wight jail. Only authorised staff at Parkhurst would have been in charge of the template key from which a copycould have been made.
Hampshire's Assistant Chief Constable, John Wright, who is heading the inquiry, said that he could "not rule out" the possibility of the men receiving assistance from prison staff.
Mr Wright was speaking on the second day of the hunt that has brought 200 additional police officers on to the Isle of Wight to continue the search for the escaped men. Helicopter searches, house-to-house inquiries, searches of sparsely- populated areas of the island, and continuing sea searches of vessels ferrying between the mainland and the island, all continued yesterday.
Although facing a third night at large, Mr Wright said he had not ruled out the possibility the men were still on the island.
Aircraft - specially equipped with infra-red sensing devices - have formed part of the police operation. Mr Wright said that given the data from the infra-red search, he believed the men were not sleeping rough, and had, if still on the island, received
help to hide.
The police operation, however, is not being confined to the Isle of Wight. Other forces throughout the UK have been informed and have mounted their own operations.
The prospect that the men may have gone south, heading for France, and not gone back on to the British mainland, appears to have been ruled out.
The three men - convicted murderers Keith Rose, 45, and Andrew Rodger, 44, and Matthew Williams, 25, convicted of conspiring to cause explosions and with administering poison and causing arson - were last seen in Parkhurst's gymnasium area at 6pm on Tuesday night. The police were notified they had gone missing at 8.13pm.
Mr Wright said that with radar records plotting the journeys of small unidentified craft leaving the island, he was confident they had not left the island after the alarm was raised.
A police search and inquiry is also being conducted on the inside of Parkhurst by the investigation of the Prison Service's head of security, Richard Tilt. Mr Tilt will today spend his third day at the prison continuing his inquiries.
The brother of one of the escaped men urged his brother to give himself up. Peter Rose said that he believed the escape could be linked to his brother's wish to highlight his case.
It also emerged yesterday that a book on the history of the Isle of Wight prison, Parkhurst Tales, by former inmate, Norman Parker, was in circulation among current inmates. The book gives details of a prison escape that uses master keys.Reuse content