AUGUSTA — Maine voters approved a conservation borrowing package Tuesday but the fate of two other bonds remained uncertain.

Although unofficial returns from 81 percent of state precincts showed majorities for passage, the margin of support was narrow.

Tuesday’s balloting on bonds was divided into three parts, with voters given an opportunity to approve or reject $55 million in bonding for research and economic development, $43.5 million for upgrades at educational institutions and $35.5 million for natural resource initiatives.

Question 2 — designed to provide $50 million through a Maine Technology Institute competitive fund for biotechnology, aquaculture, and marine, composite materials, environmental and other forms of technology, and $5 million in low-interest loans for business and agricultural development — was backed by 51 percent to 49 percent with 504 of 626 precincts reporting, according to unofficial returns.

A similar 51 percent majority favored Question 3 — the $43.5 million education bond issue.

It earmarked $23 million for building renovations and improvements of the University of Maine System campuses, $15.5 million at Maine Community College System campuses and $1.5 million at Maine Maritime Academy, with the remaining funds going to grants and loans — $1.5 million – for school units for repairs and renovations and to programs — $2 million — to revitalize downtown areas, historic and cultural sites and libraries.

As widely expected, Question 4 — which included $17 million for the Land for Maine’s Future program, $7.5 million for state parks and historic sites, $5 million for river-based community and economic development projects and $3 million for working waterfront preservation — won strong support with 63 percent approving.

The Question 4 proposal additionally called for $1.5 million to be channeled to an agricultural water source development grant program and for $1.5 million to be placed in an existing Municipal Investment Trust Fund.

In an off-year election with even a tribal racino proposal generating relatively little interest, the bond proposals did not spark much debate.

Less than five months after approving the first $131 million piece of a $295 million three-part state borrowing package, Mainers went to the polls Tuesday to decide the fate of the second and largest piece worth $134 million.

Back on April 4, a bipartisan deal on new borrowing between majority Democrats and minority Republicans won overwhelming approval in the full Legislature.

Needing two-thirds majorities in both chambers to pass, the bond package was backed on final votes of 138-6 in the House of Representatives and 33-0 in the Senate.

Provisions called for the $295 million to be divided for three separate statewide referendum votes in June and November of this year and June of 2008.

The overall three-piece $295 million borrowing package bears an estimated interest cost of nearly $84 million over the life of the proposed 10-year bonds.

The $134 million amount proposed Tuesday carried an estimated interest cost of $40.5 million, according to state Treasurer David Lemoine. In June, voters approved a pair of bond issues totaling $131 million to support transportation and make the state’s water cleaner.

A nearly $113 million bond issue for improvements to highways and bridges, airports, public transit facilities, ferry and port facilities and bicycle and pedestrian trails passed by 83,477 to 33,486. And an $18.3 million bond issue to support drinking water programs and the construction of wastewater treatment facilities was approved by 74,893 to 41,483.

Next June, voters are to be asked to pass judgment on a final part of the overall package worth $29.7 million, most of which would be for more transportation projects. A smaller amount, $6.7 million, would be raised for a variety of environmental initiatives, including hazardous waste site clean-up and fish hatchery upgrades.