At least 70 people are feared to have died in a fire at the besieged headquarters of the Branch Davidian sect near Waco, Texas.
The fate of the cult‘s leader, David Koresh, is still unknown.
The White House said the blaze had been started deliberately by those inside after the FBI began a dawn assault.
Tear gas canisters and stun grenades were fired into the cult’s fortified compound and an armoured vehicle moved in to demolish the walls.
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Three hours later they broke down the main entrance.
At one point reports said the cult members had agreed to come out but then reneged on the deal.
When the fire started at around 1200 local time (1800GMT) several children were believed to be inside with David Koresh and his followers.
By the time firefighters arrived the fire had taken a firm hold on wooden buildings inside the compound.
The fire worsened when the cult’s store of munitions exploded.
Eight cult members escaped but David Koresh is not believed to be among them.
Orders from God
The cult’s buildings been surrounded since February when four agents with the Bureau of Alcohol, Tobacco and Firearms (ATF) were killed as they attempted to arrest Mr Koresh on firearms charges.
It was hoped Mr Koresh would give himself up last week but he sent FBI agents a message saying he had not yet received his orders from God.
The Branch Davidians descend from a breakaway group from the Seventh Day Adventist Church.
President Bill Clinton said yesterday he had had advance warning of the assault on the compound.
But the president added that newly-appointed Attorney-General Janet Reno made the decision to begin the operation.