Democratic candidate for U.S. Senate Elizabeth Warren has reported an impressive fundraising haul for the second quarter of 2012.

In a release Monday, Warren announced that she raised $8.67 million in April, May and June. The campaign said it was her best fundraising quarter to date, and beat the year's first-quarter take by $1.7 million.

The Associated Press adds:

The campaign says more than 80 percent of the donations during the second quarter were $50 or less. A full breakdown of the fundraising is not expected until later in the month.

The campaign said it now has $13.5 million cash on hand.

Incumbent Sen. Scott Brown has not yet released his second-quarter fundraising figures. The Boston Globe reports that candidates must file reports by Sunday.

In the first quarter, Warren out-raised Brown, $6.9 million to $3.4 million, but Brown had about $4 million more cash on hand then.

Through the first quarter, the Senate race was the most expensive in the country.

Update at 3 p.m.: Maurice Cunningham, political science chair at the University of Massachusetts Boston, called the amount astounding, especially in light of the controversy over Warren's Native American heritage:

At the time when this heritage issue arose, oddly enough that issue has had no resonance at all in polling numbers, but it appears to have spurred her fundraising efforts, and I think some of this is in response to what Democrats perceive as a smear against her.

In a statement to WBUR's Monica Brady-Myerov, Brown's campaign criticized Warren for dependence on out-of-state donations: