FRISCO, Texas — Three firefighters and seven police officers were hospitalized after responding to a three-alarm chemical fire at a pool supply store in Frisco this week.

A fire and explosion occurred at Texas Pool Supply on John W. Elliott Drive on Wednesday at approximately 8:12 a.m. after an employee noticed a “vapor” in the building.

Frisco Fire Chief Chief Lee Glover said the 10 first responders were transported to Medical City Plano as a “precautionary measure” because they “developed symptoms they didn’t start the day with.” He did not elaborate on what those symptoms were, but the City of Frisco says those injured are in stable condition.

The cause of the fire is currently under investigation.

Frisco Fire Department Fire Marshal Kelly Kistner said chlorine, trichlor and sodium — also known as “pool shock” — were involved in the fire. Kistner is inquiring into whether a pallet of chemicals stored outside of the building could have caused the fire.

Common health effects from exposure to gases from chemicals like chlorine include irritation of the eyes, skin and throat, according to the Environmental Protection Agency.

In a statement to Spectrum News 1, U.S. EPA Region 6 spokesperson Joe Robledo said the Frisco Fire Department’s hazmat team was conducting air monitoring Wednesday and did not detect a hazard as of 9:27 a.m. The EPA is monitoring the situation and is in communications with the Texas Commission on Environmental Quality (TCEQ).

As first responders worked to put out the blaze, a shelter-in-place order was issued at approximately 8:25 a.m.

In total, 78 first responders — including those with Frisco Fire, Frisco Police and Frisco Public Works departments — were at the scene. The fire was called “out” by 9:28 a.m. and the shelter-in-place order was lifted.

The Little Elm Fire Department also responded to the scene and The Colony, Plano, Prosper and McKinney Fire Departments provided mutual aid.