Final opinion polls showed Brundtland's lobby had rallied strongly and was now neck and neck with the "No" side whose lead appeared to be fading.
On the second and final day of voting, a poll by the Scan-Facts institute published in the daily Verdens Gang showed EU supporters ahead for the first time in the month-long campaign, by 50.7 percent to 49.3.
A poll by MMI in the Dagbladet daily forecast a dead heat and a Nielsen Norge survey in Arbeiderbladet predicted a "No" win by 52 to 48 percent.
A majority of Norway's 3.2 million voters have been widely projected to oppose membership. But their lead in opinion polls has gradually shrunk.
Full results are expected Tuesday.
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