The seven University at Buffalo students sickened by exposure to carbon monoxide build up in a campus dormitory have recovered, a UB official said Monday.

“They are all fine, back in classes today, no after-effects,” said Joseph Brennan, associate vice president for university communications.

Meanwhile, the university is fixing the problem that caused the gas build up and installing new detectors in the building, Brennan said.

The Richmond Quad on the UB North Campus in Amherst was evacuated late Sunday after firefighters detected a carbon monoxide leak caused by an industrial style hot water tank that was not venting properly.

The tank was shut down and contractors were on campus Monday to fix the problem, Brennan said.

The leak was discovered after it sickened two UB students, who drove themselves to a hospital, where officials then notified university police of a possible carbon monoxide leak, Brennan said. Two more students were taken to a hospital by ambulance, while three others were treated at the scene, Brennan said.

UB thought it had carbon monoxide detectors plugged into outlets on the ground floor near the tank.

“When maintenance people went to look for them, we couldn’t find them,” Brennan explained on Monday. “I don’t know if they were moved by residents or if they were taken out of the wall.”

The university plans to replace the heat and smoke detectors it has hardwired throughout the building with units that also detect carbon monoxide, Brennan said.

In the meantime, the university on Monday plugged in more carbon monoxide detectors at the Richmond Quad.

“The safety of our students is top priority,” Brennan said. “We’re glad no one was seriously hurt. This is a very rare incident. We can’t remember when we had a carbon monoxide leak in any university facility.”