Two women in their early 20s were found dead inside a car after they apparently gassed themselves in Japan's latest suicide pact, police said Thursday.

Investigators discovered two empty bottles that contained a bathwater additive and detergent, leading them to suspect that the two mixed the two liquids to generate toxic hydrogen sulfide gas.

The two elementary school classmates were identified as 21- and 22-year-old women from Namegawa, Saitama Prefecture.

The two women were found Tuesday morning inside a car parked near the bank of the Arakawa River in the Kawara-Aketo district of Kumagaya.

"I got sick and tired of thinking about my future," said a note found in the vehicle.

A suicide Website carried a story about how to use toxic gas to commit suicide, police said.

In a related development, police yesterday confirmed that a suicide web site was involved in the deaths of four people whose bodies were found in a car on Monday in Hokkaido.

At least two of the four people found dead -- an Osaka man and a woman from Saitama Prefecture -- came in contact through an online suicide site, police said. The other two victims, two women from Hokkaido, used a similar means to get in touch.