Japanese authorities say they have released 14 crew members of a Chinese fishing trawler seized last week in the East China Sea.
But the captain of the vessel remains in custody following the incident, which happened in disputed waters.
Prosecutors have until 19 September to decide whether to lay formal charges against him.
China has made repeated protests over the incident and warned that it could harm bilateral ties.
The Chinese fishing boat reportedly rammed Japanese coast guard patrol boats which had been trying to intercept it.
he incident occurred off an island closer to Taiwan than to Japan, and claimed by both Japan and China.
Summoned
On Sunday Chinese diplomat State Councillor Dai Bingguo warned Tokyo to make a "wise political decision" over the matter.
China has cancelled a series of diplomatic negotiations with Japan over oil and gas fields in the region in protest.
Chinese officials have also called in Japanese Ambassador Uichiro Niwa for talks four times over the incident - most recently in the early hours of Sunday morning.
"It was regrettable that Ambassador Niwa was summoned at such late hours," Japan's top government spokesman, Yoshito Sengoku, said.
He also criticised Beijing for linking the gas talks with the incident, describing them as "totally separate issues".
The freed crew members are reported to have flown back on a chartered flight to Fuzhou via Naha in Okinawa.
The vessel will also be released and sailed back to China by a substitute crew, Japanese officials said.
The area where the Chinese trawler was seized on Tuesday is close to uninhabited islands, known as Senkaku in Japan and Diaoyu in China, which are controlled by Japan but also claimed by China and Taiwan.
