Police in Rostock, Germany, have discovered a weapons cache including knives, chemicals, and flammable liquids in the homes of two left wing extremists.

Rostock police searched an apartment in Hohenfelde and a garage in Bad Doberan over the weekend belonging to two men, aged 30 and 26, who are part of the left wing extremist scene. Several weapons were found at the two locations which authorities believe would have been used against police at the upcoming G20 summit, Die Welt reports.

A variety of knives, batons, a baseball bat, and illegal fireworks were found. Police say they also discovered bottles and cans they believe were filled with a flammable substance that would have likely been thrown at police.

Gas masks were also present as well as several containers of unknown chemical agents.

Both men were arrested after the raids, but the 26-year-old was subsequently released whilst the 30-year-old remains in custody. The man held will be released on July 10th, two days after the end of the G20 meeting, according to police.

Investigators are looking into bringing about potential charges against the two men for the formation of a terrorist group and noted that both were from Germany’s growing left wing extremist scene.

Police have said the left wing extremist scene has become much larger and much more violent in recent years. Thomas Rath, chief of the Göttingen police forces, expressed shock last year at the ferocity of left wing violence against his officers.

Some cities in Germany have become hubs for left wing extremism like Leipzig where extremists committed 22 acts of politically motivated violence in 2016. Some of the incidents involved violence toward politicians from the anti-mass migration Alternative for Germany (AfD) party including the torching of members’ cars.

The German capital of Berlin has also become home to left extremist groups called “autonomous groups” who illegally squat in buildings in the city. On several occasions, police have tried to evict the extremist squatters only to be met with violence.

Most recently, police tried to evict extremists from a shop known as “Friedel 54” in the Neukölln district. Authorities say the left wing agitators connected a live power line to the metal door knob of the building in an attempt to electrocute and harm officers. Police countered this by turning off all of the building’s electricity before their raid.