The investigation into the root cause of an estimated $2 million shortfall in the Board of Education's current budget continued Friday.

That's when more figures were presented by Elio Longo, the school district's business manager, to the school board's ad hoc committee probing the recently revealed shortfall, in an attempt to track down what went wrong.

But there was still confusion over why it happened and why the school board and other municipal officials weren't made aware sooner that there might be fiscal problems, in particular with a spike in the number of large claims in the board's health insurance fund, resulting in additional costs of about $1.35 million.

It was a "clear screw-up that year," Superintendent of Schools Elliott Landon said during the meeting of the board's Health Insurance Fund Review Committee meeting Friday morning in Town Hall. He said decisions were made "on bad information" and "that won't happen again."

"We did make mistakes," said school board member Brett Aronow, the committee chairwoman. At one point, she said the board also seems to have "double counted what we expected to save and that was a mistake."

Board of Finance member Tom Lasersohn questioned Longo about projections made by Segal Consulting, the school district's insurance consulting firm, that might have led to the shortfall. In particular, he wanted to know about projections made for large claims on the health insurance fund.

Longo said there was an increase in the number of large claims over the previous year, which the consultants based their projections on.

In a memo to Longo, Segal Consulting said: "Budget projections are completed using the most recent enrollment and claims experience available at the time of the projection. Since there are variables such as increased large claim activity and claims volatility that cannot be foreseen, Segal recommends margin be added to claim projection to protect against these fluctuations."

The memo said Segal had recommended a safety margin of $772,000 be included in the budget for this fiscal year. That recommendation, however, was not followed by school officials.

Selectman Helen Garten asked why there was a spike in large claims.

"You can't predict two heart transplants and one liver transplant," said Landon. He added the person who was responsible for keeping track of that budget -- Nancy Harris, the former business manager, "is no longer here." Harris, who had been the district's assistant superintendent for business, retired at the end of the last academic year.

Representative Town Meeting member Jack Klinge suggested the committee invite Harris to one of the ad hoc meetings to see "what was going on in her mind. He said she's a resource that can provide explanations and help resolve questions."

The full Board of Education will meet at 7:30 p.m. Tuesday in the cafeteria at Staples High School. The insurance consultants will be at that meeting to help answer "any outstanding issues," said Aronow. But Lasersohn suggested it might be better to meet with the consultants in a more informal format, like Friday's meeting.

Landon suggested that if Lasersohn has specific questions that he forward them to Longo who will email them to Segal Consulting.

As the school board grapples with the deficit in its current budget, Landon recently unveiled a $110.9 million budget he proposes for 2014-15.

That spending plan proposes a 6.5 percent boost in spending over the current $104 million budget, and more than 2 percent of the hike is allocated to cover the gap in this year's budget.

Landon has also included $742,600 in the proposed budget's health and medical insurance account -- as a claim fluctuation margin, or safety net -- to address future, unanticipated health expenditures that are being blamed for this year's shortfall.