South korean military has lifted the highest alert "Jindogae1" near the northern border area as no signs of intrusion from the Democratic People's Republic of Korea (DPRK) were found, Yonhap news reported Wednesday, citing military sources.

The military issued earlier on Wednesday morning the alert after finding an unidentified object in the border, according to the report. A soldier, serving on the front line in Hwacheon-gun, Gangwon-do, northeast of Seoul, threw a grenada after finding a suspective object in a border fence with the DPRK at about 2:30 am

The soldier might mistakenly took wild animal as DPRK soldier, and South Korean troops didn't find any sighs of intrusion after searching this area thoroughly, the military sources said.

Jindogae1 alert is the highest level alert by South Korean military. South korean troops were also issued an similar alert when South Korea and DPRK exchanged artillery fire near the western border island of Yeonpyeong on Nov. 23, 2010, which resulted in the death of four South Koreans.