Edgartown firefighters quickly extinguished a grass fire at South Beach Friday night begun by unknown revelers setting off fireworks.

“It was put out quickly . . . . there were a sizeable number of fireworks going off,” fire chief Peter Shemeth said Saturday morning. He said the blaze covered an area about 30 feet by 30 feet in the grass near the rest rooms at the popular Atlantic-facing beach.

No one was hurt and it was not known who started the blaze, the chief said, noting that Friday had been a busy day for calls as the Vineyard filled up with cars and people on the day before the Fourth of July holiday.

In the afternoon Friday Edgartown police and The Trustees of Reservations closed Norton Point Beach to oversand vehicles due to overcrowding. Heavy traffic impeded a response by Oak Bluffs EMS to a car fire on Beach Road.

Chief Shemeth, who was preparing for a long day Saturday morning with thousands expected to descend on Edgartown for the parade and fireworks, had a small bit of advice for people on Island for the holiday.

“A little bit of common sense,” he said.