The commander of the Tanjungbalai Asahan naval base in North Sumatra province said authorities initially found three boats overloaded with passengers anchored in the waters of Kuala Bagan Asahan village Tuesday afternoon and were later informed of a fourth vessel.

"When we checked out [three] boats, we found that they brought illegal [Indonesian] workers from Malaysia," Lt. Col. Bagus Badari was quoted as saying by detik.com Wednesday.

Officers who questioned the passengers were told that another boat would dock soon.

"We chased the [fourth] ship and seized it," Badari said, adding that members of two crews were arrested.

He said that a total of 89 people -- 67 men, 21 women and a toddler -- were found on the vessels and have been handed over to the immigration agency, while the crews remain in detention for further investigation.

According to the Indonesian Agency for Placement and Protection of Migrant Workers, there are around 1.3 million illegal Indonesian migrant workers in Malaysia.

Lacking the required official documents for travel and employment, they resort to illegal methods of transportation -- which can pose threats to their lives -- while leaving and returning to Indonesia.

On Saturday, Indonesian police seized a ship before it could transport 21 Indonesian illegal migrants from Teluk Nibung district in North Sumatra to Malaysia.

Dozens of illegal Indonesian workers lose their lives annually in boat accidents blamed on overcrowding and lack of vessel maintenance and safety supervision.

In November last year, an overloaded boat sank off Riau Islands province, killing 54 illegal migrants.