The result of Poland's knife-edge presidential election was still uncertain as of Monday morning, with the National Electoral Commission expected to hold a news conference at 0600 GMT and late polls indicating a win for incumbent Andrzej Duda.
The poll by Ipsos combines exit poll data with official results for 90% of the polling stations that took part in the exit poll and showed Duda, an ally of the ruling Law and Justice (PiS) party, winning 51.0% of the vote.
The poll has a margin of error of one percentage point.
Poland's electoral commission is expected to hold a press conference later on Monday, according to an Electoral Commission statement.
Earlier, the Commission said it would not announce partial results as it has done in the past, but only the final result - possibly on Monday. Its press office was not available for comment on Monday morning.
Poland's opposition Civic Platform (PO) grouping, whose candidate Rafal Trzaskowski was seen as having 49% in the late-night poll, said it was collecting information about what is says were voting irregularities.
"We are gathering information and signals about different irregularities and we are still only talking about polls and only a percentage of results from the National Electoral Commission so we don't have a full picture of the situation," Tomasz Siemoniak, a PO member of parliament told Reuters.
Analysts said the election could be contested at the Supreme Court by either camp, given how close the result is expected to be.
When asked about the possibility of questioning the result, Siemoniak pointed to issues already noted by the media with Poles abroad not receiving their voting packages in time.
"The registration problems, the late election packages and the situation yesterday in Split, (Croatia) where at 10pm there was a six-hour line, according to what citizens who were waiting shared. This paints a picture of unpreparedness," he said.
PiS officials did not immediately respond to requests for comment. The foreign ministry was also unavailable for comment.
The election was the first time all voters had a choice to cast ballots by mail, a change in rules necessitated by the coronavirus pandemic.