Updated: 1:12 p.m.

The Denver Police Department has asked all officers to be on the lookout for “stockpiles and caches of supplies” that violent protesters could use during the Democratic National Convention, with a list of items ranging from cases of nails to city maps.

The American Civil Liberties Union of Colorado released the internal memo Wednesday, expressing objections to some of the items listed. ACLU officials plan to hold a news conference on the subject Thursday.

Denver Police spokesman Sonny Jackson said all the items listed have been used at least once during violent protests and called the memo an “awareness flyer.”

“We’d be remiss as a police department if we were not on the lookout for what might be disruptive,” he said. “It does not say stop or detain. It just says be aware.”

The memo reports that between 20,000 and 50,000 protesters are expected at the convention and warns officers that demonstrators may use “abandoned buildings, homes, camping facilities, secluded woods and farm fields to store their supplies.”

Among the items listed are metal and plastic shields, helmets, protest sign handles (“perfect for swinging at first responders”), hand-held FRS radios, and chemicals. The memo also mentions maps, giving the explanation that they are “frequently used by violent protester[s] to plan direct actions against conventioneers.”

“Small amounts of these items would cause no concern but all first responders need to be alert for medium and large numbers of these items that seem out of place for its location,” the memo reads. “This could indicate the stock piling of supplies to be used against first responders.”

Anything suspicious should be reported to the department and the Colorado Intelligence Analysis Center, according to the memo.

Jackson said he wasn’t aware of police finding anything troubling, and he said that most protest groups have made clear that they would be peaceful during the convention.

In a news release, the ACLU cited one activist who was questioned by an officer because bricks were delivered to her home.

“Although the bricks were acquired for masonry repairs, Denver police accused the activist of ‘stockpiling’ the bricks for the DNC,” the news release reads. The activist will speak at Thursday’s news conference, but ACLU officials did not release her name Wednesday.