Prices on some computer memory chips have almost doubled in recent weeks, and one reason is an explosion at a Japanese plastics factory that makes a compound used in the chips. But some computer industry executives say the prices probably will drop as fast as they rose once alternative sources for the plastic are found.

The July 4 fire destroyed the Sumitomo Chemical Co. plant in Nihama, which supplies 60 percent of the epoxy resin used to manufacture DRAM -- dynamic random access memory -- computer chips.

Leading U.S. manufacturers say they have adequate supplies of the material to make the computer chips for several months, but are scrambling to determine what to do if there's a shortage later.

In effect, some computer industry analysts say, the prices are rising in anticipation of a shortage, not because one exists. Those analysts and others in the industry say they're confused about what role the explosion is playing in the steep price increases in memory chips on the informal "spot" market, which supplies many small computer manufacturers.

"Everybody's trying to figure out what to do," said Angela Hatfield, spokeswoman for Motorola Inc., a top U.S. maker of memory chips. "We're still assessing the effects of the explosion to see how our products would be affected."

"I've never seen such a situation where it's so hard to get reliable information," said one knowledgeable industry executive who declined to be named. "It's frustrating... . Companies are trying to find alternatives {for the compound}, and they're saying, 'What's the next step we take?' "

"Presently, National Semiconductor is able to supply our customers' current and historic run rates," said Roberta Silverstein, a spokeswoman for National Semiconductor Corp., which makes memory chips. "We don't have enough information to know what the fire will mean. ... We can only guesstimate what it means."

Prices for the computer chips have been rising for months, mostly because of increasing demand and the trend in upgrading the power of personal computers, industry executives said. Now some retailers are telling customers that the fire is why DRAM chips had increased from about $30 a megabyte to as much as $80 a megabyte.

Sumitomo has said it wants to rebuild its plant, but that could take up to a year.

Some U.S. chemical companies that were in the epoxy resin market but exited it in recent years have expressed interest in returning, in the wake of the Japanese explosion. But profit margins are tiny in the business, and entrants must undergo a thorough process of ensuring quality controls in their work, since even the most minuscule impurities in a computer chip can ruin it.

Staff writer Michael D. Shear contributed to this report.