By Patryk Wasilewski

WARSAW--Some Polish rate setters are worried the strengthening zloty could hurt exports and extend deflation, minutes from the central bank's April meeting showed Thursday.

The stronger Polish currency against the euro could hurts exporters' earnings by making their goods more expensive in the eurozone, Poland's main foreign market, while deepening deflation by lowering the domestic prices of imported goods.

The rate-setting panel kept borrowing costs at a record low of 1.5% earlier this month and the minutes show that changing the level wasn't discussed.

Poland has been in deflation since July 2014 with the consumer price index declining 1.5% annually. The country's economic recovery has continued at a robust pace, however, with expansion last year reaching 3.4%, and rate setters expect further acceleration in coming quarters, the minutes showed.

The Polish zloty has strengthened nearly 8% against the euro since the middle of January as foreign investors are lured to the local market by higher interest rates and a robust economic outlook.

Earlier in April, the euro bought less than 4 zlotys for the first time since the middle of 2011 and some analysts expect the Polish currency to strengthen more as the European central bank's quantitative easing gathers speed.

Write to Patryk Wasilewski at patryk.wasilewski@wsj.com