WELLINGTON, New Zealand (AP) — The families of 29 men killed 18 months ago when an explosion ripped through a New Zealand coal mine say they are abandoning their campaign to get the remains returned.

Since the explosion, the families have lobbied both the government and successive owners of the Pike River mine to mount an operation to recover the entombed bodies.

Bernie Monk said Wednesday that an assessment by new mine owners Solid Energy indicates the old mine shaft remains dangerously full of methane. He said the families don't want to risk any more lives in a recovery operation, and are coming to terms with the bodies remaining in the mine.

Monk's 23-year-old son Michael died in the November 2010 disaster.

Solid Energy bought the bankrupt mine this month.

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