They're issuing the warning after at least one person, a woman in her 80s, fell victim to the scam.
"She's out $500. Our detective division is looking into it, see if we can identify them and see if we can make a case on them," West Memphis Police Assistant Chief Robert Langston said.
While police work the case, they said be on lookout for a scam like this, often targeting the elderly.
This victim, now out hundreds of dollars, was approached at her home earlier this week for work on her trees.
"(They) quoted her a price of $250 and got the job done, then two or three of them came to her door," Langston said.
They wanted more money.
"Then jumped the price up to $500," Langston said. "It turns into a bait-and-switch. $250 sounds like a good price. They're intimidated. They're scared. They just want them off their porch."
The victim in the scam writes a check, and the crooks immediately take it to the bank and cash it before a stop payment can be made.
Langston said people in the city of West Memphis should check for a privilege license from anyone asking to do this type of yard work.
"They'll give them a permit, and they'll also give them a sticker to put in their window that our citizens can look at and make sure that they are licensed to do business in West Memphis," Langston said.
Another piece of advice is to make sure the people doing work are insured and get an estimate in writing before any work is completed.
West Memphis Police said they will be checking on people they see doing this kind of work and will be issuing citations if they're not following the rules.
They're asking anyone who sees someone operating without a privilege license to contact the police department at 870-732-7555.