Ten students and one adult were taken to the hospital after falling ill during a concert rehearsal at the Wentworth School in Scarborough Thursday morning.

The first sign that something was wrong came when a student passed out on the risers in the cafeteria, where 120 third and fourth graders were rehearsing, Superintendent Diane Nadeau said at a news conference Thursday afternoon. Other students on stage then began to complain of respiratory symptoms.

School staff called 911 just after 10 a.m. and ambulances from multiple towns were sent to the school to begin treating students, police and fire officials said in a statement. The school was evacuated and students were walked to the high school while sick students and school staff were evaluated. All 11 patients were released from the hospital as of 4 p.m. on Thursday.

The school has both carbon monoxide and fire detectors, and no gases or other issues were detected inside the school, Fire Chief Rich Kindelan said. The school is looking into whether the temperature on the stage and limited ventilation in the space might have caused the illnesses, the department said in a statement Thursday afternoon.

Kindelan said during the news conference that fire officials had inspected the building twice for several gases. There were no reports of a smell and the cause of the illnesses is still under investigation, he said.

Wentworth serves about 700 students in grades 3 to 5 and has more than 100 staff members.

All on-duty and some off-duty Scarborough firefighters responded to the scene with other agencies, Kindelan said. Ambulances from Scarborough, Falmouth, Biddeford, Buxton, Portland and Northeast also responded and there was still a large presence of first responders at the school late Thursday morning.

About a dozen firefighters stood outside the entrance of the school around 11:15 a.m. and some staff members appeared to go back inside. One employee said officials had been looking for a gas leak but had not found any signs of one.

Students and staff returned to the building and classes resumed as normal around noon, Nadeau said.

At the high school, a line of parents waiting to pick up their children moved slowly. Students dismissed to their parents came out of the building without their backpacks.

Maura Reminga, who was standing in line to pick up 10-year-old Leah and 9-year-old Austin, said she received an automated call from the school which was “a bit alarming.” Her mind went to the possibility of an active shooter or bomb threat, she said. But after seeing an email from the school that said students fell ill, she was relieved that her children weren’t in danger.

Maria Camp said she heard in group chats with parents that there had been a gas leak at the school, but officials at the school hadn’t told parents exactly what happened. She said her high school daughter was able to see her 10-year-old son, Henry, after he had evacuated and confirm that he was OK.

Camp said she’s grateful for Scarborough’s strong community and, despite some chaos in picking up her child, she has faith in school officials.

OTHER INCIDENTS

Thursday’s evacuation comes a few months after other schools in the area reported closures and incidents related to potential gas leaks.

In November, Yarmouth High School was evacuated after several students fainted — but no issues were found after a series of air quality tests. South Portland Middle School reported two strong gas odors in January, but no leaks were found. District officials later said the propane smell could have been related to a malfunction in the school’s natural gas system.