TEPCO sent carbon-based workers down to the Torus Rooms of Reactors 2 and 3 on June 6 to measure the water levels. No information about how long the work took, but the maximum radiation exposure for the workers was 6.49 millisieverts for going into both Reactors 2 and 3. No information about how many workers (or whose workers) TEPCO sent in. Probably the company sent in its own employees because of the high levels of radiation.
The last time the workers went near the Torus Rooms of Reactors 2 and 3 was on March 14, 2012. Six TEPCO workers spent total of 28 minutes in the reactor buildings with the radiation levels in the basements (where the Torus Rooms are located) that ranged from 15 to 160 millisieverts/hour (inside the Reactor 2 Torus Room). At that time, they couldn't enter the Reactor 3 Torus Room because the door was bent. Judging by the radiation levels in front of the Reactor 3 Torus Room door that were more than twice as high as those of the Reactor 2 Torus Room, we can guess the levels inside the Reactor 3 Torus Room were much, much higher:
The water levels in "O.P" (Onahama Peil) are indicated in the first slide below, but if the mid point of the torus is OP1900 and the water levels measured are about OP3000 (as per the last slide), and the mid basement level is OP4000, the picture is not exactly to the scale.
From TEPCO's Photos and Video Library, 6/7/2012: