Within 30 days of the date of filing the petition with the county elections official of the principal county, the county elections officials of the affected counties shall examine the petition and ascertain whether or not the petition is signed by the requisite number of voters within the county. When the county elections officials of the affected counties have completed their examination of the petition, they shall each attach to the petition their certificates, properly dated, showing the results of the examination, and if from the examination they shall find that the petition is signed by the requisite number of voters residing within the boundaries of that portion of the proposed district within the affected county, or is not so signed, they shall certify the petition as sufficient or insufficient, as the case may be, and the certificates shall forthwith be transmitted to the county elections official of the principal county.