More than 50 fires believed set by the Iraqis are burning unchecked at various oilfields throughout Kuwait, sending up a blanket of thick black smoke that could obscure Iraqi military targets from allied warplanes, Pentagon officials say.

At a Pentagon news briefing Tuesday, Rear Adm. Mike McConnell, director of intelligence for the Joint Chiefs of Staff, said the cause of the fires is uncertain, although he said the Iraqis have placed explosive charges on many Kuwaiti oil wells."There is an advantage, from their point of view, of starting a fire," McConnell said. "It creates smoke. Smoke would obscure the ground (and) make it difficult for us to find targets. . . . We're watching that. It's a difficult problem."

But McConnell also raised the possibility that allied air strikes aimed at knocking out the Iraqis' ability to use the oilfields for refueling may have sparked the fires. He did not say when the fires started, nor did he reveal specific locations for the blazes.