WARSAW (Reuters) - Care home resident with learning difficulties were found with cards instructing them to vote for Poland’s ruling party in Sunday’s European Parliament election, police said on Wednesday.

An official at the polling station in the eastern village of Tykocin noticed that residents had been given instructions on pieces of paper to vote for candidates from the ruling Law and Justice (PiS) party, a police spokesman said.

The spokesman said an investigation into the case was under way, but it had yet to be established who wrote the cards. The spokesman said a handwriting expert would help police with their inquiries.

A PiS spokeswoman could not be reached for comment. The care home did not respond to a request for comment. Polish media reported the residents had difficulties with reading, writing and communication.

PiS surged to a clear victory in Sunday’s vote, a stamp of approval for the party’s nationalist, eurosceptic platform before a national election later in the year.

The ruling party won 75.6% of the vote in the Tykocin municipality, according to Poland’s electoral commission.

The central electoral commission referred queries to the regional office, which did not answer calls.