The herbal supplement kava is no longer approved for sale in Canada, Health Canada announced Wednesday after conducting a nine-month assessment of the popular relaxant.

"There is an immediate stop sale action and recall on all products containing kava," said Health Canada spokeswoman Micheline Ho.

All such products must immediately be pulled from the shelves of all stores, she said.

The herb had been marketed as the natural alternative to sedatives and sleeping pills, but Health Canada officials say there is strong evidence to suggest that it can cause liver damage in some users. There have been four such cases reported in Canada, said Ms. Ho.

That risk is too great to allow the herb to be sold in the country, Ms. Ho said.

Wednesday's ban follows a Health Canada warning issued in January. France and Switzerland issued similar warnings last year, after the death of kava user from liver failure. Many European countries have now placed all-out bans on products containing the herb.

The therapeutic products directorate for Health Canada has been studying documentation from Europe concerning kava, at the same time formulating its own data, said Ms. Ho.

"We have enough information to say there does appear to be a serious concern here," Ms. Ho told reporters at an Ottawa press conference Wednesday.

Kava is derived from a leafy plant that grows in the Pacific and it enjoys wide use in that part of the world where it is called kava-kava. In Canada it is sold in capsule form or as a tea; Pacific islanders also use it in that latter form, often for ceremonial occasions.