Hundreds of German police on Wednesday entered a forest that protesters are trying to stop from being chopped down for a coal mine.
Police said the officers were protecting workers from energy company RWE who plan to start clearing obstacles from the floor of Hambach forest. They were also searching for dangerous objects or potential barricades.
RWE wants to starting cutting down half of the ancient forest next month to expand a nearby lignite strip mine.
The plans have enraged environmentalists, who want Germany to stop extracting and burning coal. Some have been camping in the forest for years in protest.
Two women were detained and a suspicious device was being examined by explosives experts, said Aachen police spokeswoman Petra Wienen.
Police also posted images on Twitter showing a tire fitted with long spikes that was seized during the search. Wienen said some officers had urine and feces thrown at them, but nobody was injured.