ST. LOUIS — St. Louis City police and fire leaders are asking parade-goers to be on the lookout for tools of potential disruption — namely, PVC pipes protesters could use to chain themselves together — and to call 911 if they spot any at the July 4 Celebrate STL parade downtown.

“We have gathered intelligence to suggest that protestors might disrupt the parade,” Police Chief Robert Tracy said Wednesday.

Officials are looking to prevent a repeat incident of what happened at the STLPride parade on Sunday, where pro-Palestine protestors stopped the parade procession with a “sleeping dragon tactic,” by forming a human chain, connected by metal chains inside PVC pipes. Protestors were given three warnings to disperse before they were cut apart by fire department officials and arrested.

The police department has also tweeted photos of PVC pipe under the headline “see something, say something,” telling people to report “something suspicious” by calling 911 or telling an officer.