BORKEN, West Germany (AP) _ A prosecutor on Monday promised a full probe of the Borken mine explosion, and a national television network said he was looking into whether a flame from a cigarette lighter sparked the disaster.

Rescue workers early Monday found the body of another miner, bringing the number of confirmed dead to 46.

Mine owners again defended the rescue operation following the disclosure that radio contact was made with six miners hours after the blast but then cut off when a radio operator told them to stop sending signals.

The owners of the mine acknowledged Sunday that a radio operator told the six miners to stop sending messages, believing they were another search team.

Heinz Cramer, a technical director for Preussen Elekta, the company that owns the mine, said Monday that failure to recognize the sound - two hammers banged together by the survivors - as a sign of life had not diminished the rescue effort.

''We knew that the area (where the men were found) presented the best possibility of finding survivors, and that's where we began drilling,'' Cramer said.

The six were discovered alive on Saturday, after officials insisted there was no sign of life in the coal mine where 57 men had been trapped since Wednesday.

Prosecutors are investigating whether an open flame may have ignited the gas explosion in the Stolzenbach mine in this town 72 miles northeast of Frankfurt, the ZDF television network reported Monday.

The television said cigarette lighters were found inside the mine, but mine officials say there are strict regulations against smoking underground.

The six surviving miners had used lighters to test for the presence of the deadly carbon monoxide - an odorless and invisible gas that burns with a pale- blue flame when ignited.

They survived by finding an air pocket in a part of the mine free of the gas.

High concentrations of carbon monoxide slowed the agonizing search for the last five men still missing in the depths of the shaft. Officials said rescuers were forced to repeatedly renew their oxygen supplies.

Authorities said that because of the gas fumes, there was little chance that the missing miners would be found alive.

More details emerged about the harrowing ordeal of the survivors.

Ahmet Batkan, the Turkish immigrant among them, was quoted as saying the men had tried to pull a seriously injured comrade to the air pocket, but the man reportedly along the way.

''He died in my arms,'' Batkan was quoted as saying in the Bild newspaper.

Prosecutor Stephan Walcher in the nearby city of Kassel said a full investigation had been launched into the cause of the disaster.

''We will review all of the information being collected to determine what caused the accident and whether there are grounds for any criminal prosecution,'' Walcher told reporters at a news conference at the mine.

Officials have said the mine was regularly inspected and that all government safety regulations were followed.

Erwin Braun, head of the coal administration board in Kassel, said an explosion of such ferocity had never been recorded in the region.

He praised the rescue efforts.

News about last Wednesday's radio contact with the six survivors has sparked intense media criticism of the rescue operation.

The survivors were found after their signals were picked up by a television crew's microphone, which had been lowered into a shaft 500 feet beneath the earth.

A police spokesman in the nearby town of Dillich, who spoke on condition of anonymity, said a communications center set up after the accident received a flood of calls from people offering to help in the rescue efforts.

He said some of the callers claimed they had seen where the miners were trapped in their dreams.

''We tell the people we'll call them back if they are needed,'' the police spokesman said. ''So far, the rescue center has not asked us to.''