SEOUL (AFP) — Trash-carrying balloons sent by North Korea hit the South Korean presidential compound Wednesday, security officials told Agence France-Presse (AFP), prompting Seoul to mobilize chemical response teams in the escalating tit-for-tat propaganda war.

It is the first time the South Korean leader’s office in downtown Seoul, which is protected by scores of soldiers and a no-fly zone, has been directly hit by any of the thousands of trash-carrying balloons launched by Pyongyang since May.

“The chemical, biological and radiological (warfare) response team has safely collected the trash balloons,” the presidential security service told AFP.

“After investigation, results have confirmed that there were no danger or contamination of the object,” it said.

South Korea’s Joint Chiefs of Staff had earlier confirmed the North was once again sending the trash-carrying balloons, while Seoul city authorities also issued an alert Wednesday morning.

“If you find any fallen balloons do not touch them, and report them to the nearest military unit or police station,” it said.

According to the Yonhap News Agency, the presidential office had been monitoring the balloon in real time, and was aware of exactly where it would land.

“It is difficult to handle midair because we do not know what the balloons may contain,” a presidential official said, Yonhap reported.

“There will be no change in our policy of collecting them after they have fallen.”

The military has refrained from shooting down the balloons out of concern their contents could spread further and cause more damage, Yonhap said.

The balloons are a security issue for Seoul, but in this instance the North just got lucky, an analyst told AFP.

“It is a security problem since there are different defense facilities for the presidential complex,” said Park Won-gon, a professor at Ewha Women’s University.

“Since the balloons fly with the wind, they fall very randomly. It’s difficult to say North Korea intended to do this,” he added.