Authorities intensified their search Thursday for three crewmembers of a dredger that collided with an oil tanker in Singapore waters the previous day.

Both the ocean and aerial search areas were widened, the Maritime and Port Authority of Singapore said.

Divers recovered two bodies from the partially submerged dredger on Wednesday. Seven crewmembers were rescued by the police coast guard. Two of them were hospitalized, but one has been discharged, the maritime authority said.

Five aircraft, 29 vessels and 280 personnel from Singapore were deployed to support the search operations for the Dominican dredger JBB De Rong 19, which was moved near Pulau Senang, a small island south of the main island of the Singapore city-state.

The 26 crewmembers on the Indonesian oil tanker Kartika Segara were unhurt. The tanker reportedly suffered damage to its starboard bow, but the authority said there was no oil spill. Indonesia also sent 10 vessels to assist with the search and rescue.

The collision occurred when the dredger was transiting in a westbound shipping lane as it was entering Singapore, while the tanker was joining an eastbound lane to depart.

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

"It's what we'll call a chokepoint, but also one which is characterized by dense sea traffic," said Colin Koh, a maritime research fellow at the S. Rajaratnam School of International Studies.

When visibility is poor, "crews on watch stations may miss the other vessels, especially when you're talking about smaller ones coming your way, or right in your path," he said.