An Alaska Airlines passenger plane required an emergency landing at Modesto City-County Airport Sunday morning after a fire alarm onboard the plane began to ring.

Modesto and Ceres firefighters were sent to the airport after receiving reports of a fire inside the plane’s cargo area.

The plane landed safely at the airport just before 7 a.m. and no smoke or fire was visible from the outside, Modesto Fire Department reported.

All 62 passengers onboard were safely taken from the plane as firefighters investigated.

Investigators said the plane’s fire extinguishment system had activated, and though thermal cameras indicated positive heat signals, firefighters were unable to find signs of a fire.

The plane had departed from Sacramento and was on its way to San Diego.