John 7:45

Then came the officers to the chief priests and Pharisees.

These were the temple police, Levites under the direction of the chief priests. In verse 32 we are told that the chief priests, instigated by the Pharisees, had sent the officers to arrest him. This was the act of the Sanhedrim, and was the first official attempt to arrest him, the beginning of the course that resulted, six months later, in the final arrest, trial and crucifixion. These officers returned without the expected prisoner, and the reason was demanded by the Sanhedrim which was in session, apparently waiting for their return.