The contractor hired to carry out the final round of the Tokyo Metropolitan Government’s groundwater survey at the new Toyosu wholesale food market said Saturday it was told to use a method that deviated from previous survey practices. The ninth round of the two-year-long survey, conducted between late November and early December last year, showed higher levels of toxic substances, including benzene, than were previously recorded. The Environment Ministry’s guidelines and other rules require water samples in such surveys to be collected from monitoring wells after old water is drained. Until the eighth round, contractors in many cases took samples the day after old water was drained, while in the ninth round, the contractor collected samples on the day when the older water was removed. Water samples were collected early after the survey team was instructed to do so by metropolitan government staff, a representative of the contractor said during a hearing being conducted by a special committee of the Tokyo Metropolitan Assembly. At a news conference, the metropolitan government said it gave the instruction in view of the survey schedule. In the ninth round, the contractor also submitted for analysis samples taken from old water at a monitoring well, also at the instruction of the metropolitan government. No harmful substances were detected in the samples. The metropolitan government said it requested the contractor to take the unusual step because the well did not have enough water after the pre-survey discharge. The results of the ninth round have led the metropolitan government to order an additional survey. Results will be announced later this month. The ninth round found benzene levels in groundwater up to 79 times the national environment standard. In addition, higher than allowed levels of cyanide and arsenic were detected. During the survey from November 2014, harmful substances above the official standard were not detected until the eighth round, when elevated levels of benzene and arsenic were found. Asked about the unusual practices in the ninth round, Tokyo Gov. Yuriko Koike said she has not obtained detailed information on the matter yet. “It is necessary to confirm readings” of the additional survey, she also said. Koike last year decided to postpone the planned relocation of the landmark Tsukiji fish market to the Toyosu site, citing safety concerns.