Japanese police said on Tuesday they had identified the substance that poisoned 10 workers in northern Japan who collapsed after drinking tea and coffee at work.

Investigators found sodium azide, a highly toxic substance used to inflate airbags in cars, in one of the samples from the leftover tea, a police spokesman in the city of Niigata told a news conference.The victims fell ill and were hospitalized on Monday, suffering from vomiting, numbness in the hands and feet, and other symptoms.

Police initially said they believed they found traces of cyanide in the victims' vomit, but later retracted the report saying further tests showed no signs of the deadly substance.

Public fears stoked by the incident less than two weeks after a poisoned curry killed four people and left more than 60 others ill in western Japan prompted police to order checks on stocks of all poison products.

The National Police Agency said in a report to the Cabinet it had ordered all local authorities to check stocks of poisonous substances and tighten controls, top government spokesman Hiromu Nonaka said.

"The report said the attacks are heightening public anxieties," Nonaka told reporters.

Reflecting the nation's alarm over the two poisoning incidents, Prime Minister Keizo Obuchi's Cabinet demanded urgent police action to solve the crimes.