The Joint Admissions and Matriculation Board, JAMB, says it has yet to release cut-off marks for placements into tertiary institutions for the 2017 academic year.
Head, Media and Information, Dr. Fabian Benjamin, in a statement on Tuesday, said that the policy committee meeting responsible for the marks had not met.
"We want to appeal to all candidates to jettison such speculations and engage themselves in more meaningful ventures that would add value to their future,'' he said.
Benjamin said results of the just concluded 2017 Unified Tertiary Matriculation Examination had since been released, with a few others still being previewed.
"We want to appeal to Nigerians to understand that such candidates whose results are being previewed may not necessarily have participated in any malpractice.
"But rather, centres where they sat for the examination had issues during the conduct of examination.
"These issues were reflected on the CCTV footage and this suggests why they must be carefully investigated before releasing such results," he said.
The official said a school in Abia was discovered to have connected cables secretly to a distant hall for hired mercenaries to write for candidates.
"This is very unfortunate given the fact that the school is a missionary school and supposed to be a leading light against such vices.
"We urge candidates to note that no result will be withheld without a cogent reason as this explains why we are taking time to ensure that those who are innocent are exonerated.
"Again, candidates are advised not to patronise any centre, office or shop for any service; please visit our offices in all the 36 states of the Federation and FCT for any complaint, enquiry or assistance.
"This is also because our attention has also been drawn to an illegal centre being operated near our Ikoyi Office in Lagos with the aim of defrauding innocent candidates.
"This centre collects all kinds of fees in cash for services that are even free. The general public should note that payments for any of our services are done via our TSA account with CBN and not cash."