GUTTENFELDER/APThe average age of Japan’s population is on the rise, according to government statistics.

A Japanese man stored his mother's remains in a backpack, police discovered. And mama had company.

This isn't the first such case, and now police are searching for centenarians to see if they're really still alive. So far? Nearly 300 100-year-olds are dead or missing.

Why? Cops fear family members aren't reporting deaths on purpose in order to get their loved ones' pension payouts. 

Similar, grisly cases included the police discovering the remains of a body that was registered as being 111 years old. But the man had died nearly three decades prior, BBC reported. 

And the home address of a woman supposedly 125 years old was discovered to have been turned into a park nearly 30 years ago. 

In the latest case, police said the dead woman's 64-year-old son admitted to authorities that his mother died nine years ago. He said he couldn't afford to bury her, so he placed her in a backpack. 

Their names were not released. 

"I laid out her body for awhile, washed it in a bath, then broke up the bones and put them into a backpack," the man said, according to the AFP. 

But police are suspicious and are investigating the son for fraud because his mother continued to receive pension payments long after her death. 

The average age of Japan's population is on the rise too, which may tempt family members even more. 

According to government statistics, the country's average life expectancy for women is the longest in the world at 86.44 years old. Japanese men came in fifth place at 79.59 years old. 

There are more than 40,000 registered residents that are more than 100-years-old. 

Read more: http://www.nydailynews.com/news/world/2010/08/20/2010-08-20_son_in_japan_stores_dead_mom_in_backpack_cops_fear_many_are_hiding_dead_relative.html#ixzz0xFNa2rIs