Who is the thief?

A Japanese Military ship sailing in Pacific Ocean. Japanese captain of the ship going to take a shower. He kept his diamond chain and Rolex watch in the table shelf and went for shower and returns in 10 mins.

Now listen carefully....

When he returns both chain and watch went missing

He called the crews in the ship. There were four of them. 

1. Crew01. He the cook in the ship. Captain asked where were you last 10 mins. He answered "I was in the cold room to select the meat for the lunch."

2. Crew02. Captain repeats same question. He was the house keeping guy and he informed that he was at the top of the ship correcting the flag which was upside down.

3. Crew03: again same question. He was an engineer maintains the ship. He told that he was in generator room checking the generator.

4. Crew04. Same question repeats here also.   He was also a house keeping Crew. He told I was sleeping after the night shift.

With in 10 secs captain caught the thief. How and who is the thief?