Malacanang asked on Friday transport officials to exercise due diligence in doing their job following the sinking of a passenger ferry, leaving five people dead off Quezon province.

"We are saddened by the unfortunate incident involving M/V Mercraft 3, which capsized between Dinahican, Quezon and Polilio Island," Presidential Spokesperson Harry Roque said in a statement.

He said investigations have been launched to determine the cause of the incident.

"Investigations have started to determine what caused this sea mishap even as we call on our transport officials to exercise due diligence in the performance of their duties especially with the expected huge influx of travellers to the provinces this holiday season," he said.

Roque noted that the Coast Guard had immediately conducted search and rescue operations for the crew and passengers of the ferry following the tragedy on Thursday.

The Philippine Coast Guard has said bad weather could have caused the vessel to capsize. Celerina Monte/DMS