The bodies of Mr De Salis, who had worked in Tripoli for six years, and a woman from New Zealand were discovered by security forces near a gas and oil facility on Thursday.
The pair, described by his family as close friends, were found on a beach near the coastal area of Mellitah.
In a statement issued through the Foreign Office, Mr De Salis’s family said he had been working as a power manager for First Engineering, bringing generators to Tripoli to provide electricity.
The UK government has called on Libyan authorities to investigate the “murder” of Mr De Salis and his friend.
Of the New Zealander also found dead, a statement from the New Zealand Foreign Ministry said: “The exact circumstance of their deaths is not yet clear and will be subject to an investigation by the Libyan authorities. The deceased New Zealander was normally resident in New Zealand and was visiting Libya. The family of the New Zealander have requested privacy and asked that no further details be released publicly.”
There is still little information about four Americans detained on December 27.
The detention of four American military personnel in Libya on Friday was preceded by a confrontation at a checkpoint in which gunshots were fired and a vehicle was damaged, a witness in Libya and an Obama administration official said on Saturday.
Details about the confrontation, which occurred about an hour’s drive west from Tripoli, remained unclear. The four military personnel, assigned to the United States Embassy in Tripoli, were held for several hours and then released.
A spokesman for the United States Africa Command, which oversees military operations in Africa, declined to comment on accounts of the episode in Libya. But an administration official, who declined to be identified, acknowledged that Libyan forces had fired their weapons and that a vehicle driven by two of the Americans appeared to have been damaged.
Administration officials said they were still gathering information about the episode. But the Obama administration’s reluctance to discuss it in detail also appeared to reflect sensitivities about the United States relationship with the Libyan authorities.
The confrontation was the latest brush with danger for Americans in Libya, where the security situation has deteriorated significantly since the fall of Col. Muammar el-Qaddafi in 2011.