SINGAPORE (AP) — An oil tanker and a dredger collided in Singapore waters Wednesday, capsizing the dredger and leaving five of its crew missing, authorities said.

The Maritime and Port Authority of Singapore said the dredger was partially submerged after the collision. Seven of its crew members were rescued by the police coast guard and five were unaccounted for.

After the collision, the Dominican dredger JBB De Rong 19 was moved to near Pulau Senang, where search and rescue operations are ongoing. Singapore has deployed two tugboats, three patrol craft, seven other vessels and a Super Puma helicopter to support the operations, the maritime authority said.

The 26 crew members on the Indonesian oil tanker Kartika Segara were not hurt. The tanker reportedly suffered damage to her starboard bow.

The incident occurred about 1.7 nautical miles, or just over 3 kilometers from Sisters' Island. An investigation was ongoing.

The shipping lanes around Singapore are among the world's busiest and its navigational challenges include a narrow strait, frequently limited visibility and thousands of vessels sailing through daily.

In August, the USS John S. McCain and an oil tanker collided off Singapore, killing 10 U.S. Navy sailors. The commander of the Japan-based U.S. 7th Fleet was replaced and a ship-by-ship review was ordered in the Navy following the collision. The cause of that collision is still under invesgiation.