It's called the 'devious licks' challenge and videos tagged '#deviouslick' were viewed more than 175 million times before TikTok took them down.
Now, if you search for "#deviouslick," no results are returned and an automated message from TikTok says the phrase "may be associated with behavior or content that violates our guidelines."
What is the devious licks challenge on TikTok?
The so-called devious licks challenge on TikTok involves students stealing or vandalising school property - so you can see why the police have got involved. It started earlier in September, as kids returned to school.
Those involved have posted videos of themselves stealing all sorts of things, from soap dispensers and fire extinguishers to computers and film projectors. Others have vandalised their school.
The phrase "devious lick" and the spelling variants like "devious licks" have been removed by TikTok.
In a statement on Twitter, TikTok said: "We expect our community to create responsibly - online and IRL. We're removing content and redirecting hashtags & search results to our Community Guidelines to discourage such behavior. Please be kind to your schools & teachers."
What does 'devious lick' mean?
According to Urban Dictionary, a 'lick' is "a successful type of theft which results in an acceptable, impressive and rewarding payday for the protagonist."
Most TikTok challenges, like the Grace Kelly trend or the TikTok attractiveness scale, are harmless and fun to take part in with fellow TikTokers. And in recent months, the '#oddlysatisfying' trend has really taken off and is even credited with helping people's mental health.
However, the devious licks challenge isn't the first to turn sour.
Not long ago, the baked beans challenge saw police in the UK urging shopkeepers to ban sales of baked beans to young people, because they were buying them to put on people's doorsteps.
There was also the TikTok dry-scooping trend, which saw one girl hospitalised after suffering a heart attack.
The TikTok magnet challenge seems pretty harmless, but some have said it could be fuelling misinformation about the COVID-19 vaccine.