LONDON (AP) — Scotland said Monday it has asked Libya’s new authorities for help to catch those responsible for the 1988 Lockerbie airplane bombing, Britain’s worst terrorist attack.

The Scottish prosecutors’ office said it has written to the National Transitional Council asking for written evidence and witnesses that could aid the inquiry.

The bombing of a New York-bound Pan Am plane over the Scottish town killed 270 people, most of them American. Only one person has been convicted, former Libyan intelligence officer Abdel Baset al-Megrahi.

Scottish authorities said Monday that al-Megrahi’s trial had found that he “acted in furtherance of the Libyan intelligence services in an act of state-sponsored terrorism and did not act alone.”

It said the Lockerbie investigation “remains an open inquiry.”

Al-Megrahi was sentenced to life in jail in 2001 but released on compassionate grounds in 2009 after doctors said he was dying of prostate cancer and estimated he had three months to live.

He remains alive, though reportedly in poor health, in Tripoli.

Al-Megrahi’s release infuriated the families of many Lockerbie victims.

U.S. senators in New York have asked Libya’s transitional government to hold al-Megrahi fully accountable for the Pan Am bombing by sending him back to prison.