El Pollo Loco (LOCO) said in a regulatory filing late Monday that it received an unsolicited, non-binding takeover offer from Biglari Capital.

Biglari seeks to acquire all outstanding El Pollo Loco shares that it does not already own, the company said.

El Pollo Loco said its board is evaluating the proposal together with financial and legal advisors and has not set a timetable for any decision. It also said it entered a confidentiality agreement with Biglari that includes a customary standstill.

Shares of the restaurant chain were up more than 15% in Tuesday's premarket activity.