HANOI--A Vietnamese oil tanker with 18 crewmembers on board went missing en route to central Vietnam from Singapore, officials said Monday.

The Sunrise 689 vessel, owned by Haiphong Fisheries Shipbuilding Joint Stock Co., went missing 40 minutes after it left a Singapore port at 6 p.m. Singapore time on Oct. 2, said Nguyen Van Phuong, an official with the Vietnam Maritime Administration.

"The vessel was carrying 5,226 metric tons of oil products and should have arrived in Quang Tri province on Sunday as scheduled," Mr. Phuong told The Wall Street Journal.

A company official, who spoke on the condition of anonymity, confirmed the vessel is missing, but declined to give further details.

Pham Hien, director of the Maritime Search and Rescue Center No. 3, said Vietnamese search and rescue authorities are looking for the vessel.

"We have informed relevant agencies and are contacting other vessels that operate on the same route for information about the missing vessel," Mr. Hien said.

Mr. Phuong said it isn't yet clear what led to the vessel's disappearance, adding that piracy hasn't been ruled out.

Write to Vu Trong Khanh at Trong-Khanh.Vu@wsj.com