San Jose police on Sunday were investigating the mysterious death of a woman in Room 1912 at the downtown Hotel Fairmont and the mixture of possibly poisonous chemicals found in her room that sent nine other people to the hospital on Saturday.

Firefighters were called to the hotel around 10 a.m. Saturday on reports of an apparent suicide after a hotel staff member found a woman dead in the room and smelled a chemical odor. Neither police nor the coroner have released the woman’s name, and the chemical substance involved has not been identified.

“At this time, San Jose Police are investigating the incident at the Fairmont as an apparent suicide,” said San Jose police spokeswoman Officer Gina Tepoorten on Sunday. “We do not provide specifics on suicide incidents.”

As the first responders headed for the hotel, police dispatchers can be heard telling them that a note was found in the room that read “I committed suicide by poisonous gas. One smell and you’ll die.” It was not clear if those words were a threat or a warning for those who discovered the body.

Nine employees and guests were treated at the scene and taken to local hospitals for exposure to the chemicals, San Jose Fire Department Capt. Mitch Matlow said. Some reported feeling faint and lightheaded, or were experiencing shortness of breath, he said, but none of their injuries were believed to be life-threatening.

“Nine people were decontaminated, including seven hotel staffers and two guests,” Matlow said.

“We have identified the chemicals and turned that information over to the police and they’ve asked us not to release any more information,’’ Matlow said Sunday, adding that any health issues experienced by the nine people transferred to a local hospital by ambulance “appeared to be minor.’’

Asked whether the woman’s death was an ‘’apparent suicide’’ or not, Matlow said “we don’t know at this point whether it was a suicide or not, but it was a death by a mixture of chemicals.’’

Anita Rahman, director of sales and marketing for the hotel, said Sunday afternoon that the property’s staff was cooperating fully with local authorities and that “a formal investigation into this matter is ongoing. According to reports from the San Jose Police Department poisonous chemicals killed one woman in an apparent suicide and impacted” several other people, “prompting the evacuation of four floors. We are deeply saddened by this incident and our thoughts are with the family of the guest during this difficult time.”

Rahman added that the people impacted by the chemicals were hotel employees and all “but one have been released from a local hospital. Exposure to the unknown chemical was believed to be ‘very brief.”’

She said the impacted floors have now been reopened.

Authorities shut down Market Street between San Carlos and San Fernando streets as they investigated the incident. The street was still closed off around 5 p.m.

“More than 100” emergency workers responded to the incident, including San Jose firefighters, police officers, county firefighters, and county emergency medical services personnel, Matlow estimated.

People inside the building reported that the chemical smelled like rotten eggs, indicating it may have been hydrogen sulfide gas, Matlow said.

Hydrogen sulfide gas can cause a wide range of health effects, depending on how much of it is breathed in and for how long. Exposure to very high concentrations can quickly lead to death.

Initial reports suggested the woman found dead in Room 1912 was someone other than the registered guest, whom investigators contacted and spoke with. It wasn’t immediately clear if the registered guest and woman found inside the room knew each other.

Fire crews evacuated the 18th, 19th and 20th floors. The hotel staff shut off the hotel’s ventilation system to contain the chemical.

More than a dozen fire trucks and ambulances, including at least one hazardous materials truck, were stationed outside the hotel Saturday morning.

Five people were seen being treated by fire crews outside the hotel, one of whom was showered with water from a fire hose before being taken to an ambulance on a gurney.

The hotel’s lobby and other businesses on the first floor remained open. The building was never fully evacuated.

No firefighters were injured in the incident, Matlow said.

“The hotel is being repopulated for those who wish to return to their rooms” on floors 18 and 20, Matlow said.

The chemicals were confined to the room where the woman was found deceased.

“It stinks now but it’s not toxic,” Matlow said Saturday. “The hazard was contained to that room.”

Matlow said Environmental Logistics had been tasked with cleaning up the 19th-floor room where the incident occurred.

If you or someone you know is struggling with feelings of depression or suicidal thoughts, the National Suicide Prevention Lifeline offers free, round-the-clock support, information and resources for help. Reach the lifeline at 800-273-8255.