The light cargo and passenger M28 Skytruck plane, carrying five crew members and eight passengers, dropped out of contact midmorning about 50 minutes after taking off from Pangkal Pinang in Bangka Belitung province off the southeast coast of Sumatra island, police said in a statement. It was scheduled to land in Batam in nearby Riau Kepulauan province at 10:58 a.m.
All of those aboard the plane were policemen, according to the statement.
National Search and Rescue Agency chief Henry Bambang Soelistyo said rescuers were searching waters between Mensanak and Sebangka islands for the plane.
He said villagers found a seat and a bag containing a cellphone and police documents.
TV footage showed that police uniforms and other articles of clothing also had been retrieved from the sea.