Getting your Trinity Audio player ready...

Chicago Teachers Union president and potential mayoral candidate Karen Lewis remained hospitalized Tuesday and it’s not known when she’ll be released, a union official said.

“The reason we’ve been hesitant to come out with a bunch of statements is because we still don’t know what’s going on,” CTU Vice President Jesse Sharkey said Tuesday afternoon. “We’re still waiting for results from doctors. We want information, not speculation.”

Sharkey said Lewis “felt terrible” on Sunday, and decided to see a doctor after consulting with people she was with at the time. A number of union officials were alerted to the situation that evening, Sharkey said.

“She was ill, and she’s progressively been doing better. We just don’t know what’s going on yet medically,” Sharkey said. “We’re waiting for something more definite, and when we get it we’ll know.”

On Monday, the union said Lewis , 61, was hospitalized “after experiencing discomfort Sunday evening,” at her home. The statement said Lewis “has not suffered a stroke” but gave no other information on her health. The union has yet to say what hospital she is in.

Earlier this year, Lewis told reporters that she underwent weight-loss surgery in Mexico in March.

A fierce critic of Mayor Rahm Emanuel, Lewis has maintained steady stream of public appearances in recent weeks as she considers a run for mayor but has yet to declare her candidacy for the February election.

In addition to forming an exploratory committee and touring the city on a “listening tour,” Lewis has begun fundraising in anticipation of a possible run. She contributed $40,000 of her own money to her political fund, which she said would go toward opening a campaign office and hiring staff.

A committee of The American Federation of Teachers contributed $30,000 to Citizens to Elect Karen Lewis Mayor of Chicago fund at the end of September, according to state campaign finance disclosure reports.

Emanuel has more than $8 million in his campaign fund, but has been saddled with low job approval ratings and polls that show most Chicago voters don’t approve of how he’s handled education.

Regardless of Lewis’ decision on a mayoral bid, Monday’s news comes as the union is due to begin negotiating a new labor contract, two years after the Chicago’s first teacher strike in a quarter-century.