Officials are investigating what caused a brush fire in Prospect Park Friday night.

Flames engulfed a roughly two-acre area near the Nethermead meadow in the center of the Brooklyn park after breaking out around 7 p.m., the FDNY said. More than 100 firefighters and EMS personnel responded to the scene, with some remaining overnight in case of reignition.

It comes as weather officials extend a red flag warning for the city, cautioning about an elevated risk of brush fires through Saturday.

The city is currently in a drought watch due to minimal rain over the last month. It’s the first time the city has been under drought watch in more than 20 years.

“We are encouraging New Yorkers to not throw cigarette butts on the ground. As [a] passerby did [Friday], report any fires you see. You shouldn’t be grilling in the parks, being aware of those things,” Emergency Managment Commissioner Zach Iscol said on the scene Friday night.

“Preserving water, monitoring air quality. This is the new normal of extreme weather. It’s not something we are expecting, but it’s something we need to be prepared for,” he added.

Officials said the drought watch could escalate to a drought warning if conditions don’t change soon.

Flames were also spotted in Highbridge Park in the Bronx Friday night. That fire was also brought under control within a few hours.

From Thursday night into Friday morning, a brush fire burned just across the Hudson River in New Jersey.

There is no measurable rain in the forecast until later next week.