Eric van Lustbader, author of the Jason Bourne series of thrillers, sent out a tweet at 8:20 a.m. ET saying his editor ended up in the emergency room overnight after eating at a Manhattan Chipotle. Soon after, shares fell as much as 3.4% in premarket trading. After a number of people on Twitter grilled him for further details as to how he could know it was because of Chipotle, Lustbader said the doctor blamed “unsanitary food handling” and that the timing of the incident pointed to the restaurant.

https://twitter.com/EVanLustbader/status/751028141636915200

Chipotle, whose sales are still trying to recover from a series of food safety incidents last year, quickly sought to quell concerns another outbreak could be afoot.

“We are aware of the post made on Twitter, however there have been no reports of illnesses at any of our New York restaurants,” Chipotle spokesman Chris Arnold told Fortune in an emailed statement. “Moreover, we have excellent health department scores throughout the city, and we continue to have the highest standards of food safety in our restaurants.”

The stock pared some of its losses after Chipotle issued its statement. Shares were trading about 48% below their 52-week highs on Thursday afternoon. Van Lustbader also clarified that he did not own Chipotle stock after some people accused him of trying to manipulate the price.

While the trading swoon would arguably be an overreaction under normal circumstances, the tweet came a few months after health officials linked E. coli, Salmonella, and Norovirus outbreaks to Chipotle’s restaurants, keeping customers away in droves and sending sales and its stock plummeting.

The tweet also came just a few days after the chain’s executive who oversaw food giveaways and other sales-boosting promotions was charged with cocaine possession and went on leave.