About 80 percent of the cases of the hashtag #kyujo -- meaning rescue in Japanese -- being posted on Twitter during the deadly disaster caused by heavy rains in July were unrelated to calls for help, according to a study.

While noting that rescue calls should be made over the phone in principle, study leader Shosuke Sato, associate professor at Tohoku University, urged users not to post unnecessary tweets in emergencies. "Tweets from people who genuinely need help could be lost," he said.

(A tweet using the hashtag #kyujo, meaning rescue in Japanese)

When no other means are available, Twitter Japan recommends users add the hashtag together with their detailed situation and exact location to a call for help on Twitter.

In the research, Sato analyzed 2,171 tweets with the hashtag posted between July 6 and 8.

As of July 8, more than 80 people had died and over 50 others were missing as torrential rains caused flooding and landslides in western Japan, leaving many people stranded.

The study showed only 123 tweets, or 5.7 percent of the surveyed posts, called for help, and 213 posts, or 9.8 percent, were their retweets. Combining original tweets and retweets, they only accounted for 15.5 percent of the total.

The other 1,835 tweets, or 84.5 percent of the total, were unrelated to emergency calls for help, with some commenting on things to keep in mind when using the hashtag and others sending encouraging messages to disaster victims. There were also tweets not related to the torrential rains.

Similar trends were found during the heavy rains that fell on the northern Kyushu region in southwestern Japan in July last year.

The torrential rains in July this year hit the prefectures of Okayama, Hiroshima and Ehime the hardest. As of early October, more than 200 people had died in 15 prefectures, including those three, and hundreds of people were still in shelters.