OTTAWA — The much-delayed Air India inquiry has put off hearings once again due to legal wrangling over secret documents.

The inquiry won't resume until April 30 as lawyers continue to sort out how much of the evidence can be made public.

Spokesman Michael Tansey says the inquiry's chief counsel remains confident that the necessary evidence will be available for the commission to carry on with its work.

Former Supreme Court justice John Major, the head of the inquiry, threatened last month to shut down proceedings unless federal officials relented in their claims that key documents must be censored for national security reasons.

Major said the claims at that time were so excessive they would make the public paper trail meaningless for anyone trying to follow the investigation.

Prime Minister Stephen Harper responded by telling his national security adviser, Margaret Bloodworth, to instruct lower-level officials to adopt a less restrictive approach.

Freiman and government lawyers have said since then they are making progress.

Based on those assurances, Major had hoped to resume in mid-April, but he had to postpone his plans yet again to allow time for the documents to be shared with lawyers for the families of the victims and other interested parties.

The 1985 Air India bombing, blamed on Sikh militants based in British Columbia, took 329 lives and was the worst mass murder in Canadian history.

Only one man has ever been convicted for his role in the plot. Major is reviewing what went wrong with the investigation and trying to draw lessons for current anti-terrorist policy.