Police are investigating a second new lead in one of New Zealand's most notorious unsolved crimes - the 1984 Wellington Trades Hall bombing that killed caretaker Ernie Abbott.
Wellington Detective Senior Sergeant Simon Perry says police have received a letter from a New Plymouth woman who believes her son may have been involved in the bombing.
New Plymouth police have been sent the information and plan to interview the woman.
Mr Perry said the woman had nominated her son as a suspect because she overheard him talking about making a bomb at the time of Mr Abbott's death.
Her letter followed a tip to Wellington police last December that a daughter of a possible suspect lied during the investigation about her knowledge of the suitcase containing the bomb.
It is understood that an informant, claiming ownership of the suitcase, gave evidence pointing to her father as a possible suspect.
Lengthy police investigations have continually been hampered by the lack of a definite motive by the bomber.
An initial and obvious theory was that, because it was in a union building, the bomb was aimed at a unionist, especially as there had been a bus strike the day before.
But police concluded it would have been difficult to put the bomb together and in place in such a short time.
The light green suitcase had a small Rica banana label on it.
The suitcase - booby-trapped to go off when moved - contained the equivalent of at least 1kg of gelignite.
However, the actual explosive involved was never identified.