Jair Bolsonaro, the populist Brazilian nationalist president sometimes referred to as the "Trump of the Tropics", has accused actor Leonardo DiCaprio of financially backing the fires that have torched the Amazon rainforest in that country.
Politicians and other NGOs fiercely criticised the arrest, saying it was part of a concerted attempt by Bolsonaro's government to harass environmental groups.
"DiCaprio is a cool guy, isn't he?"
DiCaprio has been an outspoken advocate on behalf of combating climate change, posting frequently on Twitter about environmental issues, including the Amazon forest fires.
"While worthy of support, we did not fund the organizations targeted", the statement read. "The future of these irreplaceable ecosystems is at stake and I am proud to stand with the groups protecting them".
Environmental groups counter that Bolsonaro is to blame through his rollback of deforestation restrictions to spur development.
DiCaprio drew Bolsnaro's ire after his environmental organization pledged $5 million to help local groups battle the fires and remediate impacted areas.
Addressing a group of supporters on Friday, he claimed that the actor has contributed funds to groups that have lit fires in the region.
Four members of the non-governmental organisation Alter do Cho Fire Brigade were arrested on Tuesday, with police accusing them of deliberately setting fires in order to document them and drum up more donations.
They were released on Thursday on a judge's order.
Cattle ranchers, farmers and illegal loggers have long used fire to clear land in the Amazon.
This is not the first time Brazil's president has suggested, without evidence, that nonprofit groups are setting fires in the Amazon, or questioned warnings about climate change.
In August, in the midst of an global outcry over the Amazon fires, Bolsonaro blamed the "information war going on in the world against Brazil" and fired the head of the governmental space research institute that monitors deforestation. "Take pictures, make a video", the President said.
But when an annual deforestation report released in November, three months after the incident, confirmed a double-digit percent uptick in deforestation, the government acknowledged that deforestation had increased year-on-year.