SAN ANTONIO— A carbon monoxide leak led officials to evacuate a downtown hotel of more than 200 guests and staff early Sunday, including a woman and her toddler who had to be hospitalized.

Paramedics were called to the Hotel Mimosa Riverwalk just after midnight for a female guest complaining of nausea and a headache.

The 45-year-old woman and her toddler daughter had recovered by sunrise, Fire Department spokeswoman Deborah Foster said.

"It was found that they had pretty high levels of carbon monoxide in their systems," Foster said.

Fire officials moved the guests—178 adults and 28 children—to the lobby of a hotel across the street. About 33 families were moved to alternate lodgings for the night, Foster said; the rest returned to their rooms later.

Hotel employees called CPS Energy and a plumber to the scene, and the leak was contained by 3 a.m. The source of the leak was unclear.

Foster said such leaks in hotels are rare and urged anyone stricken with "flu-like symptoms" to seek medical assistance.