Embassy spokesman Jeffrey Galvin said Mexico City police informed the embassy on July 5 that the body of Lourdes Maria Rodriguez, 33, had been found in her rental car.
Galvin said an investigation of the death is being carried out by Mexico City police and prosecutors. He said he could give no further details.
Rodriguez worked for the past year as a medical assistant at the Palo Alto Center of the Palo Alto Medical Foundation, according to foundation spokesman Ben Drew.
Drew said, "She was extremely well-liked by her co-workers and the news of her death has been very difficult."
He said, "We are saddened by her passing and our thoughts and prayers go out to her family and friends."
The foundation would not give any further details about Rodriguez, including where she lived, out of respect for her family's privacy, Drew said.
The foundation is providing grief counselors for the clinic employees, he said.