PORTLAND – Soaring gas prices played a role in a 28 percent gain in ridership for Amtrak’s Downeaster during the latest fiscal year, and operators of the Portland-to-Boston service are looking at options to accommodate future growth, officials said Monday.

The ridership gain was the biggest of any Amtrak train in the period ending June 30, and revenue for the month of June set an all-time record of more than $590,000, said Patricia Quinn, executive director of the Northern New England Passenger Rail Authority.

On average an additional 947 passengers rode the Portland-to-Boston train every day, and ticket revenue grew 33 percent for the year, Quinn said.

Gas prices were a primary reason for the increase in passengers, along with a fifth daily run and added capacity on the trains, she added.

“People are viewing public transportation differently than before,” Quinn said Monday. “It’s been phenomenal. All trains are up.”

The rapid growth has the Portland-based rail authority considering all options, including negotiating with rail owner Pan Am Railways to add a sixth daily round trip, to meet demand. Pan Am Railways, formerly known as Guilford, owns the rail between Portland and Plaistow, N.H.

The Downeaster added a fifth round trip last August and added a fifth passenger car on all runs in April, but Quinn is worried that might not be enough.

“What’s going to happen is we’re going to get maxed out,” Quinn said. The early train out of Portland each morning already is running at 90 percent of capacity, and the 5 p.m. train out of Boston is typically 95 percent full, she added.

The passenger rail authority board will meet later this summer to consider options for expanding capacity, as well as for expanding the service northward to Brunswick.

Funding is no longer a big question.

Gov. John Baldacci has committed to include funding for the Downeaster in his state budget next year to make up for the loss of a $6 million federal grant that’s due to expire, said Mark Latti, spokesman for the Maine Department of Transportation.

The federal grant and $1.5 million from the state currently account for $7.5 million of the Downeaster’s annual operating budget. The rest, $6 million, comes from ticket sales.

“The governor repeatedly has said that he’s committed to making sure that the Downeaster continues to run,” Latti said Monday.

Also, the Legislature has dedicated 50 percent of revenue from the car rental sales tax – or about $3 million a year – to help the passenger rail authority pay off the debt service on the loan needed to expand the rail service northward.

As proposed, the project involves upgrading old tracks and installing new ones through Portland. The route would then run along the former St. Lawrence and Atlantic line through Falmouth, Cumberland, Yarmouth and Freeport to Brunswick.