The sun-soaked chemical spill at a chemical bank in the San Francisco Bay Area that was first reported on Wednesday is spreading rapidly, according to emergency officials.

At least 10 people have been confirmed dead, including four people who were found unconscious and a woman who was found dead after being struck by a train.

The woman was taken to a hospital with a head injury, but her condition is not believed to be life-threatening.

Sunflower County emergency management director Dan Olin said his department is monitoring the situation and will provide assistance as needed.

“We’ve been monitoring the water temperature and we’ve had some reports that it’s gotten too warm for some of the fish, which are being treated,” Olin told ABC News.

“And we have a couple of boats in there that are monitoring the weather, and it looks like it’s not going to be a very good day tomorrow, especially since we have an open lake.”

It was not immediately clear if the water was safe for drinking.

San Francisco Mayor Ed Lee tweeted: “My deepest condolences to the families of those killed in this tragic incident in our city.

Our thoughts and prayers are with all of those affected.”

The chemical spill, which occurred at the San Jose Gas & Electric Co. plant in the city’s North Beach neighborhood, was reported at about 6:15 p.m. local time on Wednesday.

San Jose Mayor Ed Lujan told ABC station KPIX that the cause of the spill was being investigated.

“Our hearts are heavy for the families who have lost loved ones,” Lujan said.

“I’m aware that there have been reports of chemical spill in the area, but we’re investigating this as quickly as we can.”

It is unclear how long the spill had been ongoing.

The Associated Press contributed to this report.