Nine-year-old climate activist Licypriya Kangujam and 12-year-old Aarav Seth were detained by Delhi Police for protesting against air pollution in Delhi outside the Parliament House.
The two were detained for 40 minutes and the Central Industrial Security Force (CISF) personnel were also called to take the protesters.
"They took her somewhere but we couldn't trace her," said a tweet from her handle, which is managed by her guardians.
The two were initially taken to the Parliament Street Police Station, but later released at Jantar Mantar by the police.
Kangujam told The Wire that the police gave her a warning and told her that she would be arrested the next time if she again held demonstrations.
"I appreciate all the police personals for treating me like as a daughter except 2-3 who warned me not to protest again at the same place," she said.
Referring to it "illegal detention", the young climate activist said, "Under what law, how a nine years old kid can be arrested or detained?"
"But I will go & protest again. This is my right to raise the voice to give us clean air to breathe. If I don't tell to our leaders then to whom I should tell? My demand is for them too," Kangujam said.
Delhi's air quality, which usually worsens in the winter season, hit an eight-month low on October 17 with stubble burning accounting for only 6% of the city's PM2.5 concentration.
The national capital recorded a 24-hour average air quality index (AQI) of 312. The last time the air quality hit such a poor level was in February with an AQI 320.