Taiwanese health officials said they created a homegrown version of Tamiflu in 18 days, despite assertions by the flu drug's producer, Roche Holding Ltd., that Tamiflu is prohibitively difficult for others to make.

Officials at Taiwan's National Health Research Institutes began looking into Tamiflu production this year. But it wasn't until late August, as concerns rose about the possibility of a large-scale outbreak of avian flu in people, that a team of researchers began working to synthesize the drug in the institute's lab. By early September, the researchers said, they had produced a batch of oseltamivir phosphate, the generic name for Tamiflu, that was chemically identical to Roche's drug and more than 99 percent pure.

The researchers said they haven't conducted clinical trials using their version of the drug.

Tamiflu, which is used to treat other types of flu, is thought by health experts to be the most effective drug in fighting avian flu, but health officials around the world have raised concerns that not enough of it would be available should the disease mutate and cause an outbreak among humans.

Avian flu has spread in recent weeks to several countries in Europe from Asia, and scientists fear that if a human form develops, it could kill or severely sicken millions. With mounting pressure from countries seeking to stockpile Tamiflu, Roche said this month that it would consider licensing other companies to make the drug.

A Roche spokeswoman said she didn't know if it were possible that Taiwan had figured out how to make Tamiflu but that it wouldn't be an issue if the island nation started producing the drug. "We've said we are open to others helping in pandemic production," she said.

The National Health Research Institutes is working with a private company, ScinoPharm Taiwan Ltd., to prepare for large-scale production, which could be ready within three to five months, an institute official said.

The Taiwanese researchers aren't the only ones to have produced generic Tamiflu. Bombay-based Cipla Ltd. announced Oct. 14 that it had made a generic version of the drug.

Taiwan's government has asked Roche to work out a licensing agreement, but Taiwanese officials have said they will produce their version of Tamiflu without permission if necessary to avoid a public health crisis.

"We cannot wait until the outbreak occurs," said Su Ih-jen, director of the National Health Research Institutes' clinical-research department. "That's too late for Taiwan."

James Hookway in Bangkok and Jeanne Whalen in London contributed to this report.

Taiwan says scientists have begun producing Tamiflu in lab conditions.