None of the sickened neighbors in Konan, southern Japan, were severely ill, although about 10 were hospitalized, authorities said. The deadly hydrogen sulfide gas escaped from the girl's bathroom window and entered neighboring apartments.
The girl's suicide Wednesday night was part of an expanding string of similar deaths that experts say have been encouraged by Internet suicide sites since last summer.
A 31-year-old man outside Tokyo killed himself inside a car early Thursday by mixing detergent and bath salts, police said. A local police spokesman refused to give further details, but Kyodo News agency reported the man put a sign reading "Stay Away" on the car window.
At a business hotel in Shiga prefecture in western Japan, a man in his 30s was found dead Thursday morning by employees who noticed a strange smell coming from his room, according to national broadcaster NHK. Shiga police said officials are investigating the incident as a case of suicide by hydrogen sulfide gas but could not elaborate.
Reports of another similar death emerged Thusday afternoon when the body of a 42-year-old woman in Nagoya, central Japan, was found in a bathtub. According to Kyodo, there was toilet cleaner and bath powder nearby, along with a sign outside that read, "Poisonous gas being emitted. Caution."
Nagoya police said they could not comment on the case, but Kyodo said that fire officials called to the scene did not detect hydrogen sulfide gas.
The method has alarmed officials because of the danger that bystanders can be hurt.
"It's easy and everyone can do it," said Yasuaki Shimizu, director of Lifelink, a Tokyo-based group specializing in halting suicides. "Also there is a lot of information teaching people how to do it on the Internet."
Police say they have not tallied the number of detergent-related suicides, but media reports suggest it has reached about 30 this year, including several cases in which others were also sickened.
The 14-year-old girl, whose name was not released by police, followed the pattern of other deaths.
She mixed detergent with a liquid cleanser in her bathroom, police said. The door was closed, and she had affixed a sign on the outside warning, "Gas being emitted," Kyodo reported.
Most of those sickened nearby complained of sore throats, and about 30 people were evacuated to a nearby gymnasium.
Hydrogen sulfide gas is colorless and characterized by an odor similar to that of rotten eggs. When inhaled, it can lead to suffocation or brain damage.
Japan's government has long battled to contain the country's alarmingly high suicide rate. A total of , giving the country the ninth highest rate in the world, according to the government.
Suicides first passed the 30,000 mark in 1998, near the height of an economic slump that left many bankrupt, jobless and desperate.
The government has earmarked $220 million for anti-suicide programs to help those with depression and other mental conditions.
Last year it set a goal of cutting the suicide rate by 20 percent in 10 years through steps such as reducing unemployment, boosting workplace counseling and filtering Web sites that promote suicide.