The San Bernardino County Fire Department rescued a woman from a narrow storm drain in downtown San Bernardino Tuesday morning.

Firefighters responded to Arrowhead Avenue and Fourth Street at about 10:20 a.m. after witnesses heard a woman calling for help from a storm drain tunnel, the Fire Department said in a news release posted to social media.

The woman, whose identity was not released, was “at the end point of the narrow concrete channel, finding she had become stuck approximately 15 feet back from the opening,” the release said.

“With no room to turn around, the patient was then coached to inch herself backwards about 20 feet, where another crew opened another access point, made entry into the pipe and assisted her to safety,” officials added.

The process lasted about 25 minutes.

The woman, who was “found unclothed above the waist,” was taken to a local hospital for evaluation, though she “had no obvious injuries.”

It remains unclear how long the woman was trapped or where she first entered the tunnel.