Cards containing the words "No more Polish Vermin" have been distributed outside homes and schools following the EU referendum.
Kathleen Gaynor said her mother found the cards, which also say "Leave the EU", outside her home in Huntingdon.
After she posted the cards on a community Facebook site, others reported they had also found them.
Cambridgeshire Police said it is investigating and is "working closely with the affected community".
Ms Gaynor said her mother, who lives in the town centre, discovered the card on her doorstep at about 09:00 BST on Friday.
"Mum came out of her door and found the card weighed down by a stone so it couldn't blow away," she said.
"Mum's neighbours are Polish so we think it might have been intended for them. She was in shock, angry and couldn't believe it."
Daniel Guz, who attended a meeting with Cambridgeshire Police, said one Polish national discovered the card on her car when she parked to collect her children from school - and another found it in her garden.
He said: "It's a very bad situation, but I'm advising people to report the cards to the police and otherwise ignore them."
The insurance broker added the Polish words on the card are a very poor translation of the English and thinks "they just put the words into Google translation".
Cambridgeshire Police said officers had interviewed a number of witnesses as part of its investigation.
Det Supt Martin Brunning said: "The production and distribution of this and any other similar material is committing the crime of inciting racial hatred which carries a maximum sentence of seven years in prison.
"Any reports of hate crime in the county will be fully investigated and it is vitally important that anyone who has received these leaflets or suffered similar abuse reports it."