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UPDATED (3:45 p.m., Wednesday): Students at Napa and Valley Oak high schools were sent home Wednesday morning after excessive chlorine ended up into the swimming pool. A power outage the night before caused pool equipment to malfunction.

Maintenance workers smelled chlorine in the pool area around 6:30 a.m. and called 911, a fire official said.

As a precaution, administrators called off school for the day. Arriving students were sent home, while earlier arrivals were sent to Memorial Stadium to be picked up by their parents, officials reported.

At 8:30 a.m., the normally bustling Napa High campus of nearly 2,000 students and staff was as quiet as a tomb. Some 200 students from Valley Oak were also sent home.

The Napa Valley Unified School District’s Education Center, located adjacent to the pool, was closed and most staff were sent home, the district said. All other district schools remained open.

Three employees of the Napa Valley Unified School District were sent to Queen of the Valley Hospital as a precaution for possible chlorine exposure, said Mark Morrison, the district’s director of secondary curriculum and instruction. No students were injured.