A sewage backup closed a Cambridge high school Wednesday, giving hundreds of students an unexpected day off.

Jacob Hespeler Secondary School was initially evacuated around 10:30 a.m. due to a mysterious odour in the school’s science labs.

Students were sent to nearby Heritage Baptist College as the stench was investigated.

“The fire department responded to investigate what the odour was, and as a result of the investigation has cleared the school,” said Jim Berry, an assistant superintendent with the Waterloo Region District School Board.

Shortly after 11 a.m., school board officials confirmed that classes were cancelled for the rest of the day as the source of the smell had been determined to be a sewage backup.

“A lot of students were talking about the sewage system and how it had leaked and was causing a hazard to students,” said Grade 12 student Mutaal Minhs.

Officials say there was a brief power disruption at the school before the stench was first noticed, but aren’t sure if the two events are connected.

“We’ll be investigating all the causes to the problem and doing our best to rectify them,” said Berry.

Jacob Hespeler is expected to reopen as normal Thursday.