"We do not know if it's the weather or something else behind it," Björn Tusås, Head of Marketing and Communications at Gävle Energy, told the paper.
Ferry services between Oskarshamn and Visby have been disrupted.
Heavy rain is expected again across Östergötland and Södermanland on Tuesday, according to the Swedish Meteorological and Hydrological Institute (SMHI). It has predicted up to 50 milimetres could fall in the next 24 hours.
A gale warning has also been issued around the islands of Öland and Gotland.
"It is verging on storm strength", Sofia Söderberg, duty meteorologist at SMHI told newspaper Dagens Nyheter.