MANILA — President Rodrigo Duterte of the Philippines says a government investigation has found that the recent sinking of a Philippine boat by a Chinese vessel in the disputed South China Sea was an ordinary maritime mishap that should not strain ties between the two countries.

His statement, made on Monday, comes amid nearly daily protests by Philippine nationalist groups over the episode. The demonstrators are pressing China to turn over the crew of the ship that rammed the smaller Philippine boat two weeks ago, sending its 22 crew members into the waters near Reed Bank before they were rescued by a Vietnamese vessel.

Reed Bank is well within the Philippines’ internationally recognized exclusive economic zone, but China claims that area and virtually all the rest of the South China Sea. The mineral-rich maritime region, a vital waterway for international shipping, is also claimed in whole or in part by the Philippines, Brunei, Malaysia, Taiwan and Vietnam.

An international tribunal in The Hague ruled in 2016 in favor of maritime claims by the Philippines, but China has ignored that decision. Beijing has instead ramped up the construction of artificial islands in the area despite agreements with some Southeast Asian countries to cease such activities.