Police in Houston, Texas responded to reports of an active shooter at Ben Taub Hospital. The hospital was placed on lockdown, and some patients were evacuated. No suspect or evidence of the shooting have been found, HPD Chief Art Acevedo told reporters.

Officers are searching the hospital, but have not found any victims so far, the Houston Police Department said.

“We have not found the suspect, and we have not found evidence of an active shooter,” Chief Art Acevedo told reporters at 3:15pm local time.

Several witnesses have described the suspect as a bald white male of unknown age, Acevedo said, but the police have not found any trace of him, or evidence of the shooting.

Incredible police presence at the hospital where an active shooter was reported. @HoustonChronpic.twitter.com/usen3FDQE2 — John D. Harden (@Jdharden) February 21, 2017

About an hour before the first reports of shots fired, St. Mark’s Episcopal School in Bellaire tweeted a picture of fifth grade students holding up paintings and posing with hospital staff. The school would not answer whether the students were still at the hospital, the Houston Chronicle reported.

5th Grade is at Ben Taub Hospital sharing their artwork with the Cariogy Clinic! @harrishealth#stmesoutreachpic.twitter.com/pekcl7IaT7 — St. Mark's (@stmeshouston) February 21, 2017

“All patients and employees [are] safe at this point,” Acevedo tweeted earlier, adding that no victims have been located, but the search continued.

Officers in the process of searching the hospital; no reports of injuries at this time #hounews — Houston Police (@houstonpolice) February 21, 2017

Ben Taub is part of the Texas Medical Center and is affiliated with the Baylor College of Medicine.