Online food delivery service GrubHub wouldn’t confirm or deny reports Friday that it plans an initial public offering next year. The Chicago-based company said it is keeping its options open as it continues to grow, according to the Chicago Tribune. Reuters earlier reported that GrubHub, which lets diners order food via the Internet or mobile phones, has selected Citigroup to lead an IPO in 2013 and is in the process of filling out the rest of its underwriting syndicate. The news agency said it talked to three sources who requested anonymity because the IPO plans are not public. GrubHub spokeswoman Abby Hunt called the report “speculation,” the Tribune said.