Firefighters from eight communities battled a 6-alarm blaze that broke out late Monday at the former Suffolk Downs racetrack.

The heavy fire was knocked down around 2 a.m., according to the Boston fire department’s Twitter account. No injuries were reported, and the cause has not been determined.

Fire departments from Brookline, Cambridge, Chelsea, Needham, Newton, Quincy and Somerville provided mutual aid to the response, which was hindered by limited water supply. Firefighters laid 1,000 feet of water lines to the site and used a thermal imaging drone to identify hot spots inside the structure, the Boston fire department reported.

Firefighters were called to the 161-acre property on the East Boston-Revere line around 10 p.m. for reports of the blaze in the grandstand building overlooking the track.

HYM Investment Group, National Real Estate Advisors and Houston-based family office Cathexis are redeveloping the site beginning with a pair of commercial buildings and a 475-unit apartment building that broke ground as part of the project’s first phase. The fire broke out less than a week after a ceremonial groundbreaking marked the beginning of the 16.2-million-square-foot redevelopment.

The final live race took place in 2019, but the grandstand building has remained open and used for simulcasting. Since the track’s closure, developers partnered with Boston-based Artists For Humanity on an installation that displayed local youths’ artwork on the four-story grandstand windows. The track has remained open to the public for recreational uses.

The fire did not affect areas of the site undergoing redevelopment, HYM Investment Group said in a statement.

This report has been updated with a statement from the developers.