than units 1 and 3. Tuesday, 22 March Smoke is still rising from units 2 and 3, but is less visible, and is theorized to be steam following operations to spray water onto the buildings. Repair work resumes, after having been halted because of concerns over the smoke; it is felt safe because no significant changes in radiation levels have occurred. Work continues to restore electricity, and a supply cable is connected to unit 4. Injection of seawater into units 1–3 continues. External power cables are reported to be connected to all six units and lighting is back on again in the control room of unit 3. Wednesday, 23 March Smoke again starts belching from reactor 3 in the late afternoon, this time black and grey smoke, causing another evacuation of workers from around the area. Aerial video from the plant shows what appears to be a small fire at the base of the smoke plumes in the heavily damaged reactor building. Feed water systems in unit 1 are restored allowing an increase in the rate that water can be added to the reactor. The Japanese Chief Cabinet Secretary also advises that high levels of radioactivity have been found in Tokyo's drinking water and that it should not be used to reconstitute baby formula as it is around twice the legal limit for children. Thursday, 24 March Seawater injection to units 1, 2 and 3 continues, and radiation levels near the plant decline to 200 μSv/h, while lighting is restored to the unit 1 control room. Three workers are exposed to high levels of radiation which cause two of them to require hospital treatment, after radioactive water seeps through their protective clothes. The workers are exposed to an estimated equivalent dose of 2–6 Sv to the skin below their ankles. They were not wearing protective boots, as their employing firm's safety manuals "did not assume a scenario in which its employees would carry out work standing in water at a nuclear power plant". The activity concentration of the water is about 3.9 GBq/L. Infra-red surveys of the reactor buildings, obtained by helicopter, show that the temperatures of units 1, 2, 3 and 4 continue to decrease, ranging from 11–17 °C, and the fuel pool at unit 3 is recorded at 30 °C. Friday, 25 March NISA announces a possible breach in the containment vessel of the unit 3 reactor, though