North Korea has again sent over trash-laden balloons over the South Korean border on Thursday morning, having launched about 420 balloons overnight.

The South Korean Joint Chiefs of Staff(JCS) said the North began to send up trash balloons again Thursday, at about 9 a.m.

Of the balloons launched the previous night, about 20 landed in Seoul and northern Gyeonggi Province.

The JCS said those balloons mostly carried scraps of paper and plastic bags, and no hazardous materials, but warned the public to be careful and not touch them.

The latest launch comes 25 days after the previous one. 

North Korea has been sending trash balloons since late May in response to anti-Pyongyang leaflet campaigns carried out by defectors’ groups in South Korea.

The JCS urges people to report any balloon sightings to a nearby military unit or police station.