JAKARTA, Nov. 2 (Xinhua) -- A boat carrying 93 people capsized off Indonesia's west Batam Island early Wednesday, leaving at least 20 dead and 34 others missing, the local and national search and rescue offices said.

The boat capsized in Tanjung Bebam waters off Batam Island after leaving from Malaysia, said Azman MP, head of emergency department of the disaster agency in Batam Island.

Extreme weather and overloading were blamed for the shipwreck, he revealed.

"Over capacity and strong winds with tidal waves were believed to be the trigger of the sea incident," Azman told Xinhua.

Meanwhile, spokesman of the National Search and Rescue Office Marsudi said a search and rescue operation for the missing was underway.

"So far, our personnel have rescued 39 people," he said.

It was not clear whether the boat is operated by Malaysian or Indonesian owners.

Boat is a favorite transport means in Indonesia, an archipelago country with over 17,500 islands.