"We have formulated plans for the inquiry phase of the investigation, which will involve more interviews.
"The investigations will determine the series of events which led up to this terrible accident."
Police said last night that they would not be releasing the name of the 4-year-old boy until all family members had been notified.
Mr Yule said the council had decided to begin its own investigation into the tragedy, which would be conducted by a person independent of the council.
He said police and the council were fully co-operating in their inquiries.
"We will launch our own investigation, principally to look at any procedures that may need to be improved on, so we can prevent anything like this happening again. Often police and government investigations can take some time, so we will carry out our own investigation to determine if we can to anything in the interim."
Mr Yule said he had "no real picture" of how the boy came so close to the tractor-mower or the events leading up to the accident.
He had yesterday met two members of the family and was offering his and the council's support to them.