US senators called on the Scottish government to disclose the Lockerbie bomber's full medical records in an attempt to understand why he was released early.
In a letter to First Minister Alex Salmond they asked for the release of all medical documentation for Abdelbaset Ali Mohmed Al Megrahi both while under Scottish care and after.
They also asked the Scottish government to issue the names, medical training and specialisations of the doctors who examined Megrahi.
The Libyan, who has cancer, was diagnosed with three months to live and was freed on August 20 last year.
The medical report which led to Megrahi being released on compassionate grounds went to Scottish Justice Secretary Kenny MacAskill on August 10 last year.
Andrew Fraser, the Scottish Prison Service (SPS) director of health and care, said in the report no specialist "would be willing to say" if a three-month prognosis was reasonable.
The four senators said that examining the Libyan's full medical records would help clarify the circumstances surrounding his release.
In the letter, signed by US senators Robert Menendez, Kirsten Gillibrand, Frank Lautenberg and Charles Schumer, they wrote: "We understand that an extensive medical record was used as the basis of the decision to release Mr al-Megrahi, but only one three-page medical document with redactions has been released by the Scottish government.
"Independent examination of Mr al-Megrahi's complete medical record is necessary in order to understand the circumstances surrounding his compassionate release.
"As you know, this matter is of the utmost importance to many Americans, especially the families of the 189 American victims aboard Pam Am Flight 103."
The Libyan is the only man convicted of the 1988 bombing of PanAm flight 103 which killed 270 people.
If Megrahi's permission is needed for the release of the information they asked the Scottish government to request permission from him to do so.
Their call yesterday came on the day Scottish Labour also asked the Scottish government to name the doctors who provided medical advice for the report, and the full facts surrounding the medical evidence of Megrahi's release.
In their letter the US senators said: "It is clear that there was no consensus among specialists treating al-Megrahi's prostate cancer that he had only three months to live."
It went on: "The lack of consensus and clarity from any of the specialists involved is very troubling, especially the lack of confidence on the part of the treating oncologist, who was the most qualified to assess the worsening of Mr al-Megrahi's condition."
US senators, led by Mr Menendez, recently launched an inquiry into the Libyan's release.
Scottish Government ministers rejected calls to appear before the US inquiry.
A Scottish Government spokesman said: "We have received the letter and will reply in due course."
He said that Dr Fraser concluded in his report to Mr MacAskill that his clinical assessment was that a three-month prognosis was a reasonable estimate.
He added: "Dr Fraser is a professional of unimpeachable integrity. It was his professional responsibility to provide the clinical assessment of Al-Megrahi's condition, and his report, which was published last year by the Scottish Government, was the medical report submitted to the Justice Secretary - along with the reports of the Parole Board and Prison Governor, which also supported a compassionate release decision.
"Dr Fraser drew on expert advice from a number of cancer specialists in coming to his clinical assessment that a three month prognosis was a reasonable estimate for Al-Megrahi - it was not based on the opinion of any one doctor."
He said that the Libyan authorities hired three doctors to assess Megrahi but that their reports played no part in the decision on compassionate release.Reuse content