BOSTON — Several sponsors of the Boston Marathon have stepped forward to donate money to those affected by the bombings near the finish line, hoping to help defray costly medical expenses and other needs.

Adidas is contributing the proceeds from online sales of limited edition T-shirts as part of its $750,000 donation, Boston Beer Co. is turning over all money raised from the sale of a special brew, and the John Hancock financial company and AT&T already have pledged $1 million each.

Two explosions at Monday’s race killed three people and wounded more than 170, many of them facing long recovery periods and high medical bills.

“You feel a little frustrated and powerless about a thing like this, initially,” Jim Koch, co-founder and chairman of the craft beer firm that makes Samuel Adams products, said Thursday. “Then you realize you can take action and you can do something and part of that is to come together as a community as Boston has to take care of the people who were so tragically impacted by those bombs.”

Hancock, the principal sponsor of the marathon, participated with Boston Mayor Thomas Menino and Massachusetts Gov. Deval Patrick in the creation of The One Fund after the explosions.

The pledges from Hancock, AT&T and Adidas were made to that fund.

“When we first talked with the mayor and the governor about this on Tuesday morning, we set a goal of raising $10 million in 90 days,” said James Gallagher, executive vice president and chief administrative officer at Hancock. “We’ve exceeded $10 million in less than 48 hours for The One Fund.”

Why such a fast and massive response?

“There is a special feeling of community around the Boston Marathon that the runners have,” Gallagher said. “The city has that and, of course, the sponsors get swept up into it beyond our own commercial interests.”

Boston Beer is giving funds to a smaller organization, the Greg Hill Foundation, which can act more quickly to address immediate needs.

“They’re already writing checks for things that some of the victims need money for, like funeral expenses,” Koch said.

His company is donating money from the sales of Samuel Adams 26.2 Brew, a limited release product sold at bars and restaurants along the marathon route, and from contributions from visitors who take free tours of the company’s Boston brewery this month.

Koch said the firm’s first big holiday after he started it was Patriots’ Day in 1985, the state holiday on which the marathon is held.

“I remember driving around Boston delivering beer out of my station wagon and trying to stay ahead of the marathon route,” Koch said. “We started as a small company and, just recently, we’ve gotten to the point where we could step up to be a sponsor of the Boston Marathon.”

Adidas was the official footwear and apparel sponsor of the race for the 25th time this year.

Its T-shirts with the words, “boston stands as one” are priced at $26.20 each.

“The way we saw everyone reacting really inspired us and we wanted to make sure that we also offered our part,” said Adidas spokeswoman Katja Schreiber, “and that’s why we have come up with this special edition T-shirt.”

The shirts became available on Wednesday night and there has been a “very positive response,” she said. “We will make sure to have shirts available to meet the demand.”

In a statement, Patrik Nilsson, president of Adidas America, said, “We commend Boston — and of those associated with the City and the Marathon — for their reaction to this very challenging situation. We applaud them for standing together as one on Monday and in the days which have followed.”