Transit officials voted unanimously Monday to expand and indefinitely extend a youth pass pilot program, making it open to all low-income individuals in the T service area between the ages of 19 and 25.

The move increases the maximum age range from a roughly year-long pilot with a cutoff at 21. Youth aged 18 and under do not need to be determined low-income to qualify.

The new youth pass would be administered through any of the 17 municipalities in the core service area that chose to participate.

Costing $30 after the fare hikes take effect, the youth pass will offer a significant discount of more than 50 percent off regular cost of a monthly subway pass, which will be $84.50 starting July 1.

After MBTA control board member Brian Lang proposed extending the pilot program, set to expire at the end of the month, to a full service, control board member Monica Tibbits-Nutt suggested expanding the age range upward.

“I know that we have no data on it. And I know that we have absolutely no idea how much this is going to cost. And this might be the only time that I ever push for something like that,” Tibbits-Nutt told board members. After the vote, Tibbits-Nutt reiterated to the News Service, “We have absolutely no idea what it's going to cost us,” and said, “As far as trying to service a population, there is no better policy.”

When the T board voted to hike fares an average of 9.3 percent in March, the board also made student passes valid year-round, one aspect of the pilot program. Starting in September the T plans to allow students to purchase their monthly passes through fare vending machines, and once the youth pass is implemented after Sept. 1, youth will be able to do the same, according to T spokesman Joe Pesaturo.

All youth in participating municipalities would be eligible from ages 12 to 18 as will young adults “up to 25” if they meet criteria like enrollment in food assistance or MassHealth or are enrolled in a high-school equivalency program or job training.

The particulars of the eligibility criteria still need to be worked out, according to MBTA Director of Strategic Initiatives Laurel Paget-Seekins. Pesaturo said the T is also determining whether the cutoff would be individuals' 25th or 26th birthdays.

According to the T's analysis of the pilot, if the program's age limit was still capped at 21, all the T's core municipalities participated and it gained a 20 percent participation rate, it would cost roughly $800,000.

Approved in late 2014, the youth pass pilot was originally envisioned to be offset by new revenues from universities purchasing MBTA passes in bulk, but T officials failed to secure support from local schools for the U-pass initiative.

For the pilot the T partnered with Boston, Malden, Somerville and the Chelsea Collaborative, which administered the program. The T found no evidence of fraudulent usage in the pilot, according to a presentation Monday.

Since it was established at the behest of Gov. Charlie Baker last summer, the control board has mostly focused on finding efficiencies, new revenue sources and making repairs to the current system.

Tyree Ware, a 24-year-old community organizer with Alternatives for Community and Environment who has pushed for the youth pass and against fare hikes, said he was surprised to see the age-limit increased.

“It's amazing, you know. It's great,” Ware told the News Service. Ware said he is unsure whether he would meet the income criteria himself and said he can't afford the current cost of a monthly pass.

The 17 core municipalities are Arlington, Belmont, Boston, Brookline, Cambridge, Chelsea, Everett, Lynn, Malden, Medford, Melrose, Milton, Newton, Quincy, Revere, Somerville, and Watertown, according to the T.