At least four people killed themselves Friday by inhaling fumes from a detergent mixed with other chemicals amid a wave of similar suicides that has reportedly claimed about 50 lives this month in Japan.

Authorities are alarmed by the sudden rise in such incidents — an average of two a day were reported in April — because the chemicals are easy to get and the fumes could spread to affect bystanders or rescuers.

A 47-year-old man killed himself Friday in a Tokyo luxury hotel, said Fire Department official Toshiyuki Miyake.

Officials said emergency workers also found a 29-year-old man dead in his Tokyo apartment; a man in his 50s at a public gymnasium in northern Tokyo; and a man in his 30s in an apartment in nearby Yokohama. All died after inhaling hydrogen sulfide gas, produced by mixing detergent and a bath lotion.

A riot policeman at the Narita International Airport near Tokyo also shot himself in the head in an apparent suicide Friday, said airport police spokesman Masaru Miyamoto.

The government has been battling to contain the country's alarmingly high suicide rate. The government said 32,155 people killed themselves in 2006. Japan has a population of 128 million.

"Suicides using hydrogen sulfide have surged in April," said Eri Okuda, a spokeswoman for the country's Fire and Disaster Management Agency. "It's so easy to obtain the ingredients and anyone can use them."

Fire Department spokesman Toshiyuki Miyake said the trend "initially started from Internet sites, where people exchanged information about how to do it."

"We haven't found an effective way to prevent it," he said.

The Kyodo News agency said its tally of such deaths reached at least 49 in April — after a monthly average of 3-4 earlier this year. No police figures were available.

The 47-year-old man found at The Peninsula Tokyo hotel had left a sign reading "beware of hydrogen sulfide" on the room's door, which was locked from inside, police and fire department officials said. Bottles of cleanser and liquid bath lotion were on the bathroom floor.

In the Yokohama suicide, the man was found dead in a bathroom. Rescuers rushed to his apartment after a neighbor reported an odor from the gas, which slightly sickened three neighbors and forced 70 others to be evacuated, said city Fire Department official Hiroatsu Fujii.

Hydrogen sulfide is colorless and characterized by an odor similar to rotten eggs. When inhaled it can lead to suffocation or brain damage.

Alarmed by the growing trend, the Japan Pharmaceutical Association instructed drugstores across the nation to avoid the bulk sale of the chemicals that could produce the deadly gas and to ask customers their intended use.

Annual suicides in Japan first surpassed 30,000 per year in 1998, near the height of an economic slump that left many people jobless, bankrupt and desperate.

The government has set aside $220 million for anti-suicide programs to help those with depression and other troubles.